Title of Invention	"AN EXPRESSION VECTOR"
Abstract	Provided are an expression vector for an animal cell including a promoter, a cloni ng site or a polynucleotide encoding foreign product, and a transcription terminator, all of which are operably connected each other within the expression vector, in which at le ast one copy of human &bgr;-globin MAR sequence is attached to the 31 terminal of the tran scription terminator, and a method of expressing a foreign gene using the expression v ector.

Title of Invention

"AN EXPRESSION VECTOR"

Abstract

Provided are an expression vector for an animal cell including a promoter, a cloni ng site or a polynucleotide encoding foreign product, and a transcription terminator, all of which are operably connected each other within the expression vector, in which at le ast one copy of human &bgr;-globin MAR sequence is attached to the 31 terminal of the tran scription terminator, and a method of expressing a foreign gene using the expression v ector.

Full Text	EXPRESSION VECTOR FOR ANIMAL CELL COMPRISING AT LEAST ONE COPY OF MAR DNA SEQUENCES AT THE 3' TERMINAL OF TRANSCRIPTION TERMINATION REGION OF A GENE AND METHOD FOR THE EXPRESSION OF FOREIGN GENE USING THE VECTOR TECHNICAL FIELD The present invention relates to an expression vector for an animal cell comprisi ng a nuclear matrix attachment region (MAR) element, and a method of expressing a g ene using the same. BACKGROUND ART Extensive research has been conducted into the role of matrix attachment region (MAR) DNA sequences in the regulation of eukaryotic gene expressions. A MAR seq uence (also referred to as a scaffold attachment region (SAR)) is an exemplary element used in the regulation of transcription. In general, a MAR sequence is known to be ef fective only when inserted into a host genome. It is also known that a MAR sequence, particularly one that is highly rich in AT to an extent of about 70% or greater, increases a transgene expression in an animal cell line that has been stably transformed. It is al so known that when a MAR sequence is used, the expression variability of various trans formants is low. Such a position-independent expression is believed to be due to the MAR sequence which protects inserted DNA from the intervening effect of neighboring chromatin enhancer or silencer, or inhibits methylation of the inserted DNA, thus insulati ng foreign DNA inserts from the position effect. MAR sequences are frequently used to increase expression of foreign genes in a nimal cells. For example, WO 02/1425 discloses an expression vector containing p-gl obin MAR sequence at the 5' terminal of the promoter. US 6,388,066 also discloses a promoter-driven structure containing corn ADH1 MAR DNA sequence which is located adjacent to a combined element consisting of a promoter, a nucleotide sequence opera bly connected to the promoter, and a transcription termination region. However, a DN A structure having two or more MAR DNA sequences sequentially introduced at the 3' t erminal of a transcription terminator has not been introduced so far. Even though the technologies as described above are available in the related art, there is still a demand for an expression vector that is capable of expressing foreign g enes in animal cells with higher efficiency. While investigating a method of increasing foreign gene expression, the inventors of the present invention have found that foreign gene expression is markedly increased when at least one copy of a MAR DNA sequenc e is introduced at the 3' terminal of a transcription terminator of a gene and completed t he present invention. DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a commercially available pSV-p-gal vector (Prome ga Corp., US), which contains a SV40 early promoter and a lacZ gene operably connect ed thereto; FIG. 2 is a diagram illustrating a pSVM-p-gal vector, which has one copy of hum an p-globin MAR sequence attached to the 3' terminal of a lacZ transcription terminatio n region of a pSV-p-gal vector (Promega Corp.); FIG. 3 is a diagram illustrating a pSVMM-p-gal vector, which has two copies of h uman (3-globin MAR sequences attached to the 3' terminal of a lacZ transcription termin ation region of a pSV-p-gal vector (Promega Corp.); FIG. 4 is a graph indicating results of an assay for p-galactosidase enzyme activi ty in CHO DG44 cell lines that are transfected with pSV-p-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, in a transient state; FIG. 5 is a graph indicating results of an assay for p-galactosidase enzyme activi ty in CHO DG44 cell lines that are transfected with pSV-p-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, and have resistance to G418; FIG. 6 is a graph indicating the frequency of p-galactosidase positive cells that ar e obtained as a result of ONPG (ortho-nitrophenyl-p-D-galactopyranoside) staining of C HO DG44 cell lines which are transfected with a pSV-p-vector, a pSVM-p-gal vector an d a pSVMM-p-gal vector, respectively, and have resistance to G418; FIG. 7 is a graph indicating amounts of p-galaetosidase expression, which are ca Iculated on the basis of the frequency of p-galactosidase positive cells shown in FIG. 6; FIG. 8 is a diagram illustrating a pCMV-ß-gal vector which contains an operably c onnected CMV-derived promoter, a lacZ gene, and a SV40 transcription terminator; FIG. 9 is a diagram illustrating a pCMVMM-ß-gal vector, which has two copies of human p-globin MAR sequences sequentially attached to the 3' terminal of a SV40 tran scription terminator that is located downstream to the lacZ gene of a pCMV-p-gal vector FIG. 10 is a graph indicating results of an assay for p-galactosidase enzyme acti vity against CHO DG44 cell lines that are transfected with pCMV-p-gal vector and pCM VMM-p-gal vector, respectively, and have resistance to G418; FIG. 11 is a graph indicating the frequency of ß-galactosidase positive cells that are obtained as a result of ONPG staining of CHO DG44 cell lines which are transfecte d with a pCMV-ß-gal vector and a pCMVMM-ß-gal vector, respectively, and have resista nee to G418; FIG. 12 is a graph indicating amounts of a ß-galactosidase expression, which are calculated on the basis of the frequency of ß-galactosidase positive cells shown in FIG .11; FIG. 13 is a diagram illustrating a pCMV-IgG vector, which contains a CMV-deriv ed promoter and a immunoglobulin gene operably connected thereto, and further contai ns a dhfr (dihydrofolate reductase) gene as a selective gene; FIG. 14 is a diagram illustrating a pCMVMM-IgG vector, which has two copies of human p-globin MAR sequences sequentially attached to the 3' terminal of the transcrip tion terminator (in the case of heavy chain, BGH polyA; in the case of light chain, SV40 polyA) of IgG gene of pCMV-IgG vector. The pCMVMM-IgG vector contains a dhfr gene as a selective gene; FIG. 15 is a graph indicating results of a IgG expression level measurement pert ormed after transfecting CHO DG44 cell lines with a pCMVMM-IgG expressing vector a ccording to an embodiment of the present invention, and a pCMV-IgG vector, which is a control vector, and then adding MIX to the transfected cell lines to induce amplificatio n of the genes; and FIG. 16 is a graph indicating results comparing the expression levels of IgG in th e culture fluid obtained from the experiment of FIG. 15, which are normalized to expres sion levels of IgG obtainable from 106 cells for 24 hours. DETAILED DESCRIPTION OF THE INVENTION TECHNICAL PROBLEM The present invention provides an expression vector for an animal cell that is cap able of efficiently expressing a foreign gene. The present invention also provides a method of efficiently expressing a foreign gene using the expression vector for the animal cell. TECHNICAL SOLUTION According to an aspect of the present invention, there is provided an expression vector for an animal cell containing a promoter, a cloning site or a polynucleotide encodi ng foreign product, and a transcription terminator, all of which are operably connected t 0 the expression vector, in which at least one copy of human p-globin MAR sequence is attached to the 3' terminal of the transcription terminator. The promoter according to an embodiment of the present invention may be any c onventionally known promoter. Examples of the promoter include expression vectors s uch as SV40 early promoter (e.g., a polynucleotide containing nucleotides 1 to 419 of S EQ ID N0:1), and CMV-derived promoter (e.g., a polynucleotide containing nucleotides 1 to 684 of SEQ ID NO:6). The polynucleotide encoding foreign product according to an embodiment of the present invention may be any polynucleotide that can encode a f oreign product such as a foreign protein or a foreign nucleic acid. The foreign product may be a protein such as lacZ, immunoglobulin, GCSF or EPO. The term "cloning site 11 refers to a nucleic acid sequence into which a restriction enzyme recognition site or cl eavage site is introduced so as to allow foreign genes to be inserted into a vector. According to an embodiment of the present invention, the transcription terminate r may be any conventionally known transcription terminator. Examples of the transcrip tion terminator include human growth hormone polyadenylation signal, bovine growth h ormone polyadenylation signal, and SV40 virus polyadenylation signal. The transcripti on terminator according to an embodiment of the present invention may be SV40 virus polyadenylation signal (a polynucleotide comprising nucleotides 4021 to 4156 of SEQ I DNO:1). According to an embodiment of the present invention, the term matrix attachmen t region (MAR) refers to a DNA sequence which transiently attaches a transcriptively act ive DNA loop domain to the filamentous protein network known as nuclear matrix (Pient a et al., Crit. Rev. Eukaryotic Gene Express., 1:355-385 (1991)). Many examples of th e MAR sequence are known in the related art, and one exemplary MAR sequence may be a sequence of Genbank accession number L22754 (a polynucleotide comprising nu cleotides4178 to 7142 of SEQ ID NO:1). According to an embodiment of the present i nvention, when two or more copies of MAR sequences are contained in the 3' terminal r egion of the transcription terminator, these two or more copies of MAR sequences may be connected adjacently to each other, or may be separated by a relatively short spacer region. For example, the two or more copies of MAR sequences may be connected s equentially and adjacently to each other. In addition, according to an embodiment oft he present invention, the term "3" terminal of transcription terminator" refers to the 3' ter minal of a transcription terminator, or in other words, a polyadenylation (polyA) signal. However, the 3' terminal of a polyadenylation signal is not necessarily intended to mean the exact 3' terminal of the polyadenylation signal only, and should be interpreted to en compass the downstream region of the 3' terminal that is under the influence of the poly adenylation signal. An example of the expression vector according to an embodiment of the present invention is an expression vector having any one of the nucleotide sequences of SEQ I D NOs: 1,2,5,6 and 7, or a pCMVMM-IgG expression vector having the vector map sh own in FIG. 14. A vector having the sequence of SEQ ID NOs: 1, 2, 6 or 7 is such that the polynucleotide encoding foreign product is a gene encoding lacZ, while a vector ha ving the sequence of SEQ ID NO:5 is such that the polynucleotide encoding foreign pro duct is a gene encoding GCSF. The pCMVMM-IgG expression vector having the vect or map shown in FIG. 14 is such that the polynucleotide encoding foreign product is a g ene encoding an immunoglobulin heavy chain and light chain. According to another aspect of the present invention, there is provided a method of expressing a foreign gene, comprising culturing an animal cell that is transfected with an expression vector according to an embodiment of the present invention. In the method according to the present invention, the animal cell may be any ani mal cell, and examples thereof include cells selected from the group consisting of CHO, BHK, NSO and human cells, but are not limited thereto. The animal cell may be a CH O cell. In addition, the method of culturing the animal cell may be any method that is k nown in the related art. A person having ordinary knowledge in the art would be able t o appropriately select the culturing conditions such as medium, temperature, etc., in ac cordance with the selected cell line. ADVANTAGEOUS EFFECTS The expression vector for an animal cell according to the present invention can b e used to significantly increase expression of foreign genes in animal cells. The gene expression method according to the present invention can be used to express genes in animal cells easily with high efficiency. MODE OF THE INVENTION Hereinafter, the present invention will be described in more detail with reference t 0 examples. However, these examples are provided only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention. EXAMPLES The inventors of the present invention examined the effect of a MAR element tha t is contained in an expression vector for an animal cell and is attached to the 3' termina 1 of a transcription terminator of a gene, on the expression of the gene. To this end, fir st, a vector having one or two copies of human p-globin MAR sequences inserted at a d ownstream position of a SV40 polyadenylation signal was prepared. The prepared vec tor was introduced into animal cells, and the animal cells were cultured in order to obser ve the extent of expression of the gene. EXAMPLE 1: Preparation of vector containing MAR sequence at the 3' terminal o fgene. 1. Isolation of human p-globin 5' MAR. First, HepG-2 cells were cultured, and genome DNA was isolated from the obtain ed HepG-2 cells using DNeasy Kit (Qiagen, US), according to the instruction provided b y the manufacturer. Subsequently, a polymerase chain reaction (PCR) was performed using the obtai ned genome DNA as a template, and using the oligonucleotides of SEQ ID NOs: 3 and 4 as primer, in order to amplify the 5' MAR sequence of human p-globin gene. PCR w as performed under the conditions of 35 cycles of 15 minutes at 94°C, 1 minute at 94°C 1 minute at 62°C and 3 minutes at 72°C, and another cycle of 10 minutes at 72°C. The PCR product thus obtained was inserted into a yT&A cloning vector (Yeaster n Biotech Co., Ltd., Taiwan) to prepare a yT&A/ß-globin MAR vector having the 5' MAR sequence of ß-globin gene inserted therein. The yT&A cloning vector is a TA cloning v ector designed to allow direct cloning of a PCR product without using a restriction enzy me. 2. Preparation of expression vector for animal cell containing MAR sequence at t he 3' terminal of transcription terminator of a gene. 1) Preparation of pSVM-ß-gal and pSVMM-p-gal vectors, both having SV40 early promoter. lacZ gene and SV40 transcription terminator operablv connected thereto an d having one copy and two copies, respectively, of human ß-globin MAR sequences co nnected to the 3' terminal of SV40 transcription terminator. Using a pSV-ß-gal vector (Promega, US) containing a SV40 early promoter and a lacZ gene operably connected to the promoter (See FIG. 1), an expression vector for an animal cell containing a MAR sequence at the 3' terminal of transcription terminator of a gene was prepared. First, the yT&A/ß-globin MAR vector obtained in Section 1 was treated with Bam HI and Xbal, the product obtained from the treatment was isolated by agarose gel electr ophoresis, and BamHI-Xbal product was isolated from the product obtained from the tre atment. Next, the BamHI-Xbal product was ligated to a pSV-p-gal vector (Promega, U S) that had been treated with BamHI and Xbal, and thus a pSVM-p-gal vector having o ne copy of human p-globin MAR sequence connected to the 3' terminal of the SV40 tra nscription terminator (See FIG. 2) was obtained. The nucleotide sequence of the pSV M-p-gal vector was the same as the sequence of SEQ ID NO: 1. Subsequently, the yT&A/p-globin MAR vector obtained in the above Section 1 w as treated with Xbal and Pstl, the product obtained from the treatment was isolated by agarose gel electrophoresis, and Xbal and Pstl product was isolated from the product o btained from the treatment. Next, the Xbal-Pstl product was ligated to a pSVM-p-gal v ector that had been treated with Xbal and Pstl, and thus a pSVMM-p-gal vector having t wo copies of human p-globin MAR sequences connected to the 3' terminal of the SV40 transcription terminator (See FIG. 3) was obtained. The nucleotide sequence of the p SVMM-p-gal vector was the same as the sequence of SEQ ID NO: 2. 2) Preparation of pCMVMM-ß-qal vector having CMV promoter. lacZ gene and S V40 transcription terminator operablv connected thereto, and having two copies of hum an p-globin MAR sequences connected to the 3' terminal of SV40 transcription terminat or. Using a pCMV-ß-gal vector containing CMV promoter, lacZ gene and SV40 trans cription terminator operably connected thereto, an expression vector for an animal cell c ontaining two copies of human p-globin MAR sequence at the 3' terminal of transcriptio n terminator of a gene was prepared. First, in order to insert two copies of human p-globin MAR sequences into the pC MV-p-gal vector containing CMV early promoter, lacZ gene and transcription terminator, the pCMV-p-gal vector was treated with Pmel to open the vector, and then the opened pCMV-p-gal vector was isolated and purified using agarose gel electrophoresis. Sub sequently, the opened pCMV-p-gal vector was treated with alkaline phosphatase to rem ove phosphate. After the removal of phosphate, the treatment product was heated at 65°C for 15 minutes to deactivate the alkaline phosphatase, which was then removed b y column chromatography. A pSVMM-p-gal vector was used to insert two copies of hu man p-globin MAR sequences into the opened pCMV-p-gal vector that had been treate d as described above. The pSVMM-p-gal vector was first treated with EcoRV to obtain a fragment of 5.8 kb containing two copies of human p-globin MAR sequences, and th e fragment was isolated and purified using agarose gel electrophoresis. Subsequently , the fragment containing two copies of MAR was inserted into the opened pCMV-p-gal vector with Pmel treatment. Thus, a complete pCMVMM-p-gal expression vector was obtained. FIG. 8 is a diagram illustrating the pCMV-p-gal vector, which contains CMV-deriv ed promoter, lacZ gene and SV40 transcription terminator operably connected thereto, while FIG. 9 is a diagram illustrating the pCMVMM-p-gal vector, in which two copies of h uman ß-globin MAR sequences are sequentially connected to the 3' terminal of the SV4 0 transcription terminator located downstream of the lacZ gene of the pCMV-p-gal vecto r. 3) Preparation of pCMVMM-lqG vector having CMV promoter, immunoqlobulin q ene and SV40 transcrition terminator operablv connected thereto, and having two copi es of human ß-globin MAR sequences connected to the 3' terminal of SV40 transcriptio n terminator. Using a pCMV-IgG vector containing CMV promoter, human immunoglobulin G g ene and SV40 transcription terminator operably connected thereto, an expression vecto r for animal cell containing two copies of human p-globin MAR sequence at the 3' termi nal of the transcription terminator of IgG gene was prepared. First, the pCMV-IgG vector was treated with Pmel to open the vector, and the op ened pCMV-IgG vector was isolated and purified by agarose gel electrophoresis. Next , the opened pCMV-IgG vector was treated with alkaline phosphatase to remove phosp hate. After the removal of phosphate, the treatment product was heated at 65°C for 1 5 minutes to deactivate the alkaline phosphatase, which was then removed by column c hromatography. A pSVMM-p-gal vector was used to insert two copies of human p-glo bin MAR sequences into the opened pCMV-IgG vector which had been treated as descr ibed above. The pSVMM-ß-gal vector was treated with EcoRV to obtain a fragment of 5.8 kb containing two copies of human p-globin MAR sequences, and the fragment was isolated and purified using agarose gel electrophoresis. Subsequently, the fragment containing two copies of MAR was inserted into the opened pCMV-IgG vector with Pme I treatment. Thus, a complete pCMVMM-IgG expression vector was obtained. FIG. 13 is a diagram illustrating the pCMV-IgG vector, which contains CMV-deriv ed promoter and human immunoglobulin G gene operably connected to the promoter. The pCMV-IgG vector contains dhfr (dihydrofolate reductase) gene as a selective gen e. In Fig. 13, IS stands for intronic sequence. FIG. 14 is a diagram illustrating the pCMVMM-IgG vector, in which two copies of human p-globin MAR sequences are sequentially connected to the 3' terminal of transcr iption terminator of the IgG gene (for heavy chain, BGH polyA; for light chain, SV40 pol yA) of the pCMV-IgG vector. The pCMVMM-IgG vector contains dhfr gene as a select! ve gene. In FIG. 14, IS stands for intronic sequence. EXAMPLE 2: Effect of MAR sequence attached to the 3' terminal of gene on the expression of the gene. In this example, the pSVM-ß-gal vector, pSVMM-ß-gal vector, pCMVMM-ß-gal ve ctor and pCMVMM-IgG vector prepared in Example 1 were introduced into animal cells, and the animal cells were cultured in order to examine the effect of the human p-globi n MAR sequence attached to the 3' terminal of a gene on the expression of the gene. For the control, pSV-ß-gal vector (Promega, US), pCMV-p-gal vector and pCMV-lg vect or were used. 1. Transfection of CHO cell. (1) Transfection using DOSPER (surfactant). 2 ng each of the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector were respectively co-transfected with 33 ng of pSV2neo vector (Clontech, US) into CH 0 DG44 cell lines (5x105 cells/well) using a surfactant DOSPER (Roche, Germany), acc ording to the instruction of the manufacturer. In order to perform the co-transfection, t he CHO DG44 cell lines were first washed once with a MEM-a medium containing nucl eoside but no serum, and then the cell lines were cultured in the same MEM-α medium. After 1 hour, the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector were respectively mixed with the pSV2neo vector containing a selective gene, and then with 5.3 \|j,g of DOSPER (Roche, Germany). Then, the mixtures were allowed to react at a mbient temperature for 30 minutes. After the reaction of 30 minutes, the CHO DG44 c ell lines that had been cultured in the MEM-a medium were treated with the reaction mi xtures, respectively, and the treated cell lines were cultured together with the reaction m ixtures for 8 hours. Subsequently, the culture fluid was exchanged with an MEM-a me dium containing 10% (v/v) of heat-treated FBS and nucleoside, and the culture was con tinued for another 36 hours. The transfected CHO DG44 cells were cultured again in a selective medium containing G418 (a MEM-a medium containing 10% of heat-treated FBS, 850 jag/ml of G418 and nucleoside) for about 3 weeks, and the cell line having res istance to G418 was selected. The obtained cell lines, that is, the cell lines transfected with the pSV-p-gal vecto r, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, and having resistance to G 418 were assayed, in order to examine the frequency of cells expressing p-galactosidas e and the amount of expressed p-galactosidase. (2) Transfection using calcium phosphate. 2 μg each of the pSV-p-gal vector, pSVMM-p-gal vector, pCMV-p-gal vector and pCMVMM-ß-gal vector were respectively co-transfected with 500 ng of pSV2neo vector (Clontech, US) into CHO DG44 cell lines (5x105 cells/well) using calcium phosphate. I n order to perform the co-transfection, the CHO DG44 cell lines were first washed once with a MEM-α medium containing nucleoside and 1% of FBS, and then the cell lines we re cultured in the same MEM-a medium. After 1 hour, the pSV-p-gal vector, pSVMM-p -gal vector, pCMV-p-gal vector and pCMVMM-p-gal vector were respectively mixed with the pSV2neo vector containing a selective gene, and then with calcium phosphate to f orm precipitates. The CHO DG44 cell lines that had been cultured in the MEM-α medi um were treated with the previously formed precipitates for 4 hours, and then with a 10 % glycerol solution. After the 1-minute treatment, the glycerol solution was completely removed, subsequently the culture fluid was exchanged with an MEM-a medium contai ning 10% (v/v) of heat-treated FBS and nucleoside, and the culture was continued for a nother 36 hours. The transfected CHO DG44 cells were cultured again in a selective medium containing G418 (a MEM-α medium containing 10% heat-inactivated FBS, 850 tag/ml of G418 and nucleoside) for about 3 weeks, and the cell line having resistance t o G418 was selected. The obtained cell lines, that is, the cell lines transfected with the pSV-p-gal vecto r, pSVMM-p-gal vector, pCMV-p-gal vector and pCMVMM-p-gal vector, respectively, an d having resistance to G418 were assayed, in order to examine the frequency of cells e xpressing ß-galactosidase and the amount of expressed p-galactosidase. In addition, 2.5μg of each of the pCMV-IgG vector and the pCMVMM-IgG vector were respectively introduced into CHO DG44 cell lines (5x105 cells/well) using calcium phosphate. In order to perform the introduction, the CHO DG44 cell lines were first wa shed once with a MEM-a medium containing nucleoside and 1% of FBS, and then the c ell lines were cultured in this MEM-a medium. After 1 hour, the pCMV-IgG vector and t he pCMVMM-IgG vector were respectively mixed with calcium phosphate to form precip itates. The CHO DG44 cell lines that had been cultured in the MEM-a medium were r espectively treated with the precipitates for 4 hours, and then with a 10% glycerol soluti on for 1 minute. After the treatment of 1 minute, the glycerol solution was completely r emoved, subsequently the culture fluid was exchanged with an MEM-a medium contain! ng 10% (v/v) of heat-treated FBS and nucleoside, and the culture was continued for an other 72 hours. After the 72-hour culture, the transfected CHO DG44 cells were cultur ed in a 6-well plate using a selective medium (SFM4CHO medium (Hyclone, US)) in whi ch only a cell line containing dfhr gene can grow. Subsequently, the amounts of IgG e xpression in the transfected CHO DG44 cell lines were examined. 2. Investigation of amount of B-aalactosidase expression and the frequency of B-galactosidase positive cells in cell lines respectively transfected with pSVM-ß-gal vector and pSVMM-B-aal vector and having resistance to G418. In transient CHO DG44 cells transfected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-ß-gal vector, respectively, the amounts of ß-galactosidase express! on were measured through an analysis of B-galactosidase enzyme activity. First, the c ell lines were transfected, and after 48 hours, the CHO DG44 cell lines transfected with the pSV-B-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, were w ashed twice with 1X PBS, and the cells were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were washed twice with PBS, and then a I ysis buffer (0.25 M Tris-HCI containing 0.1% of Nonidet P40, pH 8.0) was added to the cells in an amount of 200 nl per 5x106 cells. The cell-buffer mixtures were allowed to r eact at 4°C for 30 minutes. During the reaction of 30 minutes, the cell-buffer mixtures were mixed using vortex every 10 minutes. After the reaction, the cell-buffer mixtures were centrifuged at 4°C at 13,000 rpm for 10 minutes, and then the supernatants were t ransferred to new tubes. The obtained supernatants, that is, the cell lysates, were sub jected to an analysis for ß-galactosidase enzyme activity using a ▬5-Gal assay kit (Invitro gen, US) according to the instructions of the manufacturer. 10 \|o,l of each of the cell lys ates was added to a 96-well plate for EIA, and then 50 μl of a 1X cleavage solution (60 mM Na2HPO4-7H2O, 40 mM NaH2PO4-H20, 10 mM KCI, 1 mM MgSO47H20, pH 7.0) a nd 17 ul of an ONPG solution (concentration: 4 mg/ml) were added thereto, allowing the mixture to react at 37°C for 30 minutes. 125μl of a reaction stop solution was added to terminate the reaction, and then the absorbance of the reaction mixture was measure d at 420 nm. The total amounts of protein in the cell lysates were measured according to a bicinchoninic acid (BCA) method, and the p-galactosidase enzyme activities were normalized to the activity obtainable with a constant amount of protein for the analysis. FIG. 4 is a graph indicating analysis results of ▬5-galactosidase enzyme activity i n CHO DG44 cell lines in a transient state, which are transfected with the pSV-ß-gal vec tor, pSVM-ß-gal vector and pSVMM-ß-gal vector, respectively. As shown in FIG. 4, the P-galactosidase expression did not increase in the case of transfection with one copy of MAR sequence as well as the case of transfection with two copies of MAR sequence s. It can be seen from the results that, as previously reported, the MAR element does not increase expression of a gene in a transiently transfected cell, even though the gen e is connected to the MAR element. Subsequently, the ß-galactosidase enzyme activities in cell lines that were transf ected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector, respectiv ely, and had resistance to G418, were analyzed. First, 2 μg of the pSV-ß-gal vector, ß SVM-▬5-gal vector and pSVMM-p-gal vector were co-transfected with 33 ng of a pSV2ne o vector (Clontech, US) into CHO DG44 cell lines (5x105 cells/well) using a surfactant, DOSPER (Roche, Germany), according to the instructions of the manufacturer. After 36 hours of the co-transfection, the cell lines were cultured in a selective medium contai ning G418 (a MEM-α medium containing 10% of heat-treated FBS, 850 αag/ml of G418 and nucleoside) for about 3 weeks to obtain CHO DG44 cell lines having resistance to G418. The amounts of ß-galactosidase expression were measured in the CHO DG44 cell lines having resistance to G418 through analysis of p-galactosidase enzyme activity FIG. 5 is a graph indicating analysis results of p-galactosidase enzyme activity in CHO DG44 cell lines that were transfected with pSV-ß-gal vector, pSVM-ß-gal vector an d pSVMM-ß-gal vector, respectively, and had resistance to G418. As shown in FIG. 5, the amount of p-galactosidase expression increased 18- to 29-fold compared with the control, in the CHO DG44 cell lines having resistance to G418, by introducing the MAR sequence to the 3' terminal of polyadenylation signal. In particular, when two copies of MAR sequences were introduced, the increasing effect was enhanced by about 60% c ompared with the case where one copy of MAR sequence was introduced. Then the frequency of ß-galactosidase positive cells in the previously obtained C HO DG44 cell lines that were transfected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector, respectively, and had resistance to G418, were measured usi ng a ß-gal staining method. First, the cells cultured in a 6-well plate using a selective medium (a MEM-α medium containing 10% of heat-treated FBS, 850 μg/ml of G418 an d nucleoside) were washed twice with 1X PBS and were separated from the culture ves sel using a 0.25% trypsin solution. The separated cells were treated with the selective medium to deactivate trypsin, subsequently centrifuged to remove trypsin and were was hed twice with 1X PBS. After the washing, the cells were treated with a fixing solution comprising 2% formaldehyde and 0.2% glutaraldehyde at 4°C for 10 minutes to fix the c ells and were washed twice with PBS. Then, the cells were stained with ONPG, which is coloration product obtained by treating X-Gal, a substrate for p-Gal enzyme. As a re suit of the staining, positive cells turned ß-gal vector, respectively, and having resistanc e to G418 were stained with ONPG. As shown in FIG. 6, the frequency of ß-galactosid ase positive cells increased, as the MAR sequence was introduced at the 3' terminal of transcription termination region, that is, polyadenylation signal of a gene. This implies that the MAR sequence introduced at the 3' terminal of the polyadenylation signal incre ases the expression of the gene upstream thereto. Also, as shown in FIG. 6, when tw o copies of MAR sequences were introduced, the frequency of p-galactosidase positive cells significantly increased (about 90%), compared with the case where one copy of M AR sequence was introduced (about 70%). FIG. 7 is a graph indicating the amounts of ß-galactosidase expression presente d in FIG. 5, which were recalculated on the basis of the frequency of p-galactosidase po sitive cells. As shown in FIG. 7, the amount of ß-galactosidase expression per positive cell unit increased 7.4- to 8.9-fold compared with the control, as a result of introducing human ß-globin MAR sequence to the 3' terminal of the ß-galactosidase gene. In parti cular, the amount of ß-galactosidase expression increased by about 20% in the case of introducing two copies of MAR sequences, compared with the case of introducing only one copy of MAR sequence. 3. Investigation of the amount of B-qalactosidase expression and the frequency of ß-galactosidase positive cells in cell line having pCMVMM-ß-qal vector introduced and having resistance to G418. First, the amounts of ß-galactosidase expression in the cell lines which were tran sfected with the pCMV-ß-gal vector and pCMVMM-p-gal vector, respectively, and had r esistance to G418, were measured through analysis forß-galactosidase enzyme activit y. First, the G418-resistant CHO DG44 cells that had been cultured in a selective med ium for about 3 weeks after transfection with the pCMV-ß-gal vector and pCMVMM-ß-ga I vector, respectively were washed two times with 1X PBS, and the cells were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were was hed two times with PBS, then 200μl of a lysis buffer (0.25 M Tris-HCI pH 8.0, 0.1% Non idet P40) was added per 106 cells, and the cell-buffer mixtures were allowed to react at 4°C for 30 minutes. During the reaction time of 30 minutes, the cell-buffer mixtures we re mixed using vortex every 10 minutes. After the reaction, the reaction mixtures were centrifuged at 4°C and at 13,000 rpm for 10 minutes, and the supernatants were transfe rred to new tubes. The obtained supernatants, that is, the cell lysates, were then subj ected to analysis for (3-galactosidase enzyme activity using a ß-Gal assay kit (Invitrogen , US), according to the instructions of the manufacturer. 10 μl of each of the cell lysate s was added to a 96-well plate for El A, and then 50 ^l of a 1X cleavage solution (60 mM Na2HP04-7H2O, 40 mM NaH2P04-H2O, 10 mM KCI, 1 mM MgSO4-7H2O, pH 7.0) and 17 μl of an ONPG solution (concentration: 4 mg/ml) were added thereto, allowing the mi xture to react at 37°C for 30 minutes. 125 μl of a reaction stop solution was added to ter minate the reaction, and then the absorbance of the reaction mixture was measured at 420 nm. The total amount of protein in the cell lysates was measured according to the bicinchoninic acid (BCA) method, and the p-galactosidase enzyme activity was normali zed to the activity obtainable with a constant amount of protein for the analysis. FIG. 10 is a graph indicating analysis results of p-galactosidase enzyme activity i n the CHO DG44 cell lines that were transfected with the pCMV-p-gal vector and pCMV MM-p-gal vector, respectively, and had resistance to G418. As shown in FIG. 10, the amounts of p-galactosidase expression, which was connected to the CMV-derived prom oter, in the CHO DG44 cell lines having resistance to G418 increased about 6.3-fold co mpared with the control vector, as two copies of MAR sequences were introduced at th e 3' terminal of the polyadenylation signal. Next, the frequency of ß-galactosidase positive cells was investigated using the ß -gal staining method. First, cells cultured in a 6-well plate using a selective medium (a MEM-α medium containing 10% of heat-treated FBS, 850 μg/ml of G418 and nucleosid e) were washed twice with 1X PBS and were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were treated with the selective medium to deactivate trypsin, subsequently centrifuged to remove trypsin, and then washed twice with 1X PBS. After the washing, the cells were treated with a fixing solution comprisin g 2% formaldehyde and 0.2% glutaraldehyde at 4°C for 10 minutes to fix the cells and were washed twice with PBS. Then the cells were stained with ONPG, which is a color ation product obtained by treating X-Gal, a substrate for ß-Gal enzyme. As a result of t he staining, the positive cells turned blue. FIG. 11 is a graph indicating the frequency of ß-galactosidase positive cells, whic h were obtained as a result of staining the CHO DG44 cell lines, that were transfected with the pCMV-ß-gal vector and the pCMVMM-ß-gal vector, respectively, and had resist ance to G418, with ONPG. As shown in FIG. 11, the frequency of ß-galactosidase pos itive cells increased about 3.1-fold as MAR sequences were introduced at the 3' termina I of the transcription termination region, that is, the polyadenylation signal, of the gene. This implies that the MAR sequence introduced at the 3' terminal of the polyadenylatio n signal increased the gene expression, even in the case where the gene located upstr earn to the MAR sequence uses a CMV-derived promoter instead of SV40 promoter. FIG. 12 is a graph indicating amounts of ß-galactosidase expression presented i n FIG. 10, which were recalculated on the basis of the frequency of p-galactosidase pos itive cells. As shown in FIG. 12, the amounts of p-galactosidase expression per positiv e cell unit increased about 2.2-fold compared with the control, when human ß-globin M AR sequence is introduced at the 3' terminal of gene. 4. Investigation of the amount of IgG expression in cell line having pCMVMM-IgG vector introduced and cultured in a medium for screening dhfr gene CHO DG44 cells were transfected with the pCMV-IgG vector and the pCMVMM-l gG vector, respectively, and then the transfected CHO cells were cultured in a selective medium (SFM4CHO medium (Hyclone, US) containing 5% heat-inactivated and dialyz ed FBS) in which only those cell lines containing dhfr gene can grow, for 2 weeks. Su bsequently, these cell lines were inoculated onto a 6-well plate using 3 types of selectiv e media containing MTX at a concentration of 7x105 cells/ml, cultured for 3 days, and th en the amount of IgG expression in the culture fluid was measured. The selective med ia used contained 0 nM, 25 nM, 50 nM and 100 nM of MTX, respectively. FIG. 15 is a graph indicating amounts of IgG expression measured after transfec ting CHO DG44 cell lines with the pCMVMM-IgG expression vector according to an em bodiment of the present invention and a control vector pCMV-IgG expression vector, re spectively, and then inducing gene amplification by adding MIX to the transfected cell li nes. As shown in FIG. 15, the amount of IgG expression increased, as two copies of MAR sequences were introduced at the 3' terminal of the polyadenylation signal. Furl her, as the concentration of MIX increased, the rate of increase in the amount of IgG e xpression was higher for the pCMVMM-IgG expression vector compared with the contra I pCMV-IgG vector. When treated with 100 nM of MIX, the amount of IgG expression in the cells containing the pCMVMM-IgG vector increased about 6-fold, compared with t he cells containing the control pCMV-IgG vector. FIG. 16 is a graph indicating results of comparison of the amounts of IgG expres sion in the culture fluid obtained in the experiment of FIG. 15, which were normalized to the expression amount values produced by 106 cells for 24 hours. As shown in FIG. 16, in the case of the pCMVMM-IgG vector, when the cells were treated with 100 nM of MITX, the amount of IgG expression increased about 5-fold, compared with the cell line containing the control pCMV-IgG vector. It can be also seen from FIG. 16 that as the MIX concentration is increased, the rate of increase in the amount of IgG expression al so increased. This implies that during the process of gene amplification, cells containi ng the pCMVMM-IgG vector are amplified and express the IgG gene more efficiently th an the cells containing the pCMV-IgG vector. From the results of the Examples of the present invention as described above, it can be seen that when a human p-globin MAR sequence is introduced at the 3' terminal of a transcription termination signal of a gene, expression of an upstream gene located next to a promoter including SV40 promoter and CMV promoter is significantly enhanc ed. Introduction of one copy of a human p-globin MAR sequence led to a significant in crease in the expression of the upstream gene, and in particular, introduction of two cop ies of human p-globin MAR sequences led to further enhancement in the increasing eff ect induced by the introduction of one copy of the MAR sequence. This occurrence is believed to be caused by the notable reduction of the position effects by the introduced MAR sequence on adjacent nucleic acid sequences present in the host cell, but the pre sent invention is not intended to be limited to this specific mechanism. INDUSTRIAL APPLICABILITY The expression vector for an animal cell according to an embodiment of the pres ent invention can be used to significantly increase expression of foreign genes in anima I cells. The gene expression method according to an embodiment of the present invent! on can be used to express genes in animal cells easily with high efficiency. -CLAIMS- 1. An expression vector for an animal cell comprising a promoter, a cloning site or a polynucleotide encoding foreign product, and a transcription terminator, all of which ar e operably connected each other within the expression vector, wherein at least one cop y of human p-globin matrix attachment region (MAR) is located at the 3' terminal of the t ranscription terminator. 2. The expression vector of claim 1, wherein the promoter is SV40 early promoter o r CMV promoter. 3. The expression vector of claim 1, wherein the polynucleotide encoding the foreig n product is a gene encoding lacZ, immunoglobulin, GCSF or EPO. 4. The expression vector of claim 1, wherein the transcription terminator is SV40 vir us transcription terminator. 5. The expression vector of claim 1, wherein the MAR sequence is the sequence of Genbank Accession No. L22754. 6. The expression vector of claim 1, comprising a polynucleotide containing nucleoti des 4161 to 10134 of SEQ ID N0:2, in which two copies of human p-globulin MAR seq uences are connected adjacently to each other. 7. The expression vector of claim 1, wherein two or more copies of human p-globin MAR sequences are linked to the 3' terminal of the transcription terminator, and the MA R sequences are connected adjacently to each other, or are separated by a coding seq uence or a non-coding sequence. 8. The expression vector of claim 1, having any one of the nucleotide sequences S EQ ID NOs: 1, 2, 5, 6 and 7, or a pCMVMM-IgG expression vector having the vector ma p shown in FIG 14. 9. A method of expressing a foreign gene, comprising an animal cell transfecting wi th the expression vector according to any one of claims 1 to 8, which comprises a polyn ucleotide encoding the foreign protein, and culturing the transfected animal cell. 10. The method of claim 9, wherein the animal cell is selected from the group consist ing of CHO, BHK, NSO and human cells. 11. An expression vector and a method of expressing a foreign gene substantially such as herein described with reference to the accompanying drawings and as illustrated in foregoing examples.

Full Text

EXPRESSION VECTOR FOR ANIMAL CELL COMPRISING AT LEAST ONE COPY
OF MAR DNA SEQUENCES AT THE 3' TERMINAL OF TRANSCRIPTION TERMINATION REGION OF A GENE AND METHOD FOR THE EXPRESSION OF
FOREIGN GENE USING THE VECTOR
TECHNICAL FIELD
The present invention relates to an expression vector for an animal cell comprisi ng a nuclear matrix attachment region (MAR) element, and a method of expressing a g ene using the same.
BACKGROUND ART Extensive research has been conducted into the role of matrix attachment region
(MAR) DNA sequences in the regulation of eukaryotic gene expressions. A MAR seq uence (also referred to as a scaffold attachment region (SAR)) is an exemplary element
used in the regulation of transcription. In general, a MAR sequence is known to be ef fective only when inserted into a host genome. It is also known that a MAR sequence, particularly one that is highly rich in AT to an extent of about 70% or greater, increases a transgene expression in an animal cell line that has been stably transformed. It is al so known that when a MAR sequence is used, the expression variability of various trans formants is low. Such a position-independent expression is believed to be due to the MAR sequence which protects inserted DNA from the intervening effect of neighboring chromatin enhancer or silencer, or inhibits methylation of the inserted DNA, thus insulati ng foreign DNA inserts from the position effect.
MAR sequences are frequently used to increase expression of foreign genes in a nimal cells. For example, WO 02/1425 discloses an expression vector containing p-gl obin MAR sequence at the 5' terminal of the promoter. US 6,388,066 also discloses a promoter-driven structure containing corn ADH1 MAR DNA sequence which is located adjacent to a combined element consisting of a promoter, a nucleotide sequence opera bly connected to the promoter, and a transcription termination region. However, a DN A structure having two or more MAR DNA sequences sequentially introduced at the 3' t erminal of a transcription terminator has not been introduced so far.
Even though the technologies as described above are available in the related art, there is still a demand for an expression vector that is capable of expressing foreign g

enes in animal cells with higher efficiency. While investigating a method of increasing foreign gene expression, the inventors of the present invention have found that foreign gene expression is markedly increased when at least one copy of a MAR DNA sequenc e is introduced at the 3' terminal of a transcription terminator of a gene and completed t he present invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a commercially available pSV-p-gal vector (Prome ga Corp., US), which contains a SV40 early promoter and a lacZ gene operably connect ed thereto;
FIG. 2 is a diagram illustrating a pSVM-p-gal vector, which has one copy of hum an p-globin MAR sequence attached to the 3' terminal of a lacZ transcription terminatio n region of a pSV-p-gal vector (Promega Corp.);
FIG. 3 is a diagram illustrating a pSVMM-p-gal vector, which has two copies of h uman (3-globin MAR sequences attached to the 3' terminal of a lacZ transcription termin ation region of a pSV-p-gal vector (Promega Corp.);
FIG. 4 is a graph indicating results of an assay for p-galactosidase enzyme activi ty in CHO DG44 cell lines that are transfected with pSV-p-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, in a transient state;
FIG. 5 is a graph indicating results of an assay for p-galactosidase enzyme activi ty in CHO DG44 cell lines that are transfected with pSV-p-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, and have resistance to G418;
FIG. 6 is a graph indicating the frequency of p-galactosidase positive cells that ar e obtained as a result of ONPG (ortho-nitrophenyl-p-D-galactopyranoside) staining of C HO DG44 cell lines which are transfected with a pSV-p-vector, a pSVM-p-gal vector an d a pSVMM-p-gal vector, respectively, and have resistance to G418;
FIG. 7 is a graph indicating amounts of p-galaetosidase expression, which are ca Iculated on the basis of the frequency of p-galactosidase positive cells shown in FIG. 6;
FIG. 8 is a diagram illustrating a pCMV-ß-gal vector which contains an operably c onnected CMV-derived promoter, a lacZ gene, and a SV40 transcription terminator;

FIG. 9 is a diagram illustrating a pCMVMM-ß-gal vector, which has two copies of human p-globin MAR sequences sequentially attached to the 3' terminal of a SV40 tran scription terminator that is located downstream to the lacZ gene of a pCMV-p-gal vector
FIG. 10 is a graph indicating results of an assay for p-galactosidase enzyme acti vity against CHO DG44 cell lines that are transfected with pCMV-p-gal vector and pCM VMM-p-gal vector, respectively, and have resistance to G418;
FIG. 11 is a graph indicating the frequency of ß-galactosidase positive cells that are obtained as a result of ONPG staining of CHO DG44 cell lines which are transfecte d with a pCMV-ß-gal vector and a pCMVMM-ß-gal vector, respectively, and have resista nee to G418;
FIG. 12 is a graph indicating amounts of a ß-galactosidase expression, which are calculated on the basis of the frequency of ß-galactosidase positive cells shown in FIG .11;
FIG. 13 is a diagram illustrating a pCMV-IgG vector, which contains a CMV-deriv ed promoter and a immunoglobulin gene operably connected thereto, and further contai ns a dhfr (dihydrofolate reductase) gene as a selective gene;
FIG. 14 is a diagram illustrating a pCMVMM-IgG vector, which has two copies of human p-globin MAR sequences sequentially attached to the 3' terminal of the transcrip tion terminator (in the case of heavy chain, BGH polyA; in the case of light chain, SV40 polyA) of IgG gene of pCMV-IgG vector. The pCMVMM-IgG vector contains a dhfr gene as a selective gene;
FIG. 15 is a graph indicating results of a IgG expression level measurement pert ormed after transfecting CHO DG44 cell lines with a pCMVMM-IgG expressing vector a ccording to an embodiment of the present invention, and a pCMV-IgG vector, which is a control vector, and then adding MIX to the transfected cell lines to induce amplificatio n of the genes; and
FIG. 16 is a graph indicating results comparing the expression levels of IgG in th e culture fluid obtained from the experiment of FIG. 15, which are normalized to expres sion levels of IgG obtainable from 106 cells for 24 hours.
DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL PROBLEM
The present invention provides an expression vector for an animal cell that is cap able of efficiently expressing a foreign gene.
The present invention also provides a method of efficiently expressing a foreign gene using the expression vector for the animal cell.
TECHNICAL SOLUTION
According to an aspect of the present invention, there is provided an expression vector for an animal cell containing a promoter, a cloning site or a polynucleotide encodi ng foreign product, and a transcription terminator, all of which are operably connected t
0 the expression vector, in which at least one copy of human p-globin MAR sequence is
attached to the 3' terminal of the transcription terminator.
The promoter according to an embodiment of the present invention may be any c onventionally known promoter. Examples of the promoter include expression vectors s uch as SV40 early promoter (e.g., a polynucleotide containing nucleotides 1 to 419 of S EQ ID N0:1), and CMV-derived promoter (e.g., a polynucleotide containing nucleotides
1 to 684 of SEQ ID NO:6). The polynucleotide encoding foreign product according to
an embodiment of the present invention may be any polynucleotide that can encode a f
oreign product such as a foreign protein or a foreign nucleic acid. The foreign product
may be a protein such as lacZ, immunoglobulin, GCSF or EPO. The term "cloning site
11 refers to a nucleic acid sequence into which a restriction enzyme recognition site or cl
eavage site is introduced so as to allow foreign genes to be inserted into a vector.
According to an embodiment of the present invention, the transcription terminate r may be any conventionally known transcription terminator. Examples of the transcrip tion terminator include human growth hormone polyadenylation signal, bovine growth h ormone polyadenylation signal, and SV40 virus polyadenylation signal. The transcripti on terminator according to an embodiment of the present invention may be SV40 virus polyadenylation signal (a polynucleotide comprising nucleotides 4021 to 4156 of SEQ I DNO:1).
According to an embodiment of the present invention, the term matrix attachmen t region (MAR) refers to a DNA sequence which transiently attaches a transcriptively act ive DNA loop domain to the filamentous protein network known as nuclear matrix (Pient a et al., Crit. Rev. Eukaryotic Gene Express., 1:355-385 (1991)). Many examples of th

e MAR sequence are known in the related art, and one exemplary MAR sequence may be a sequence of Genbank accession number L22754 (a polynucleotide comprising nu cleotides4178 to 7142 of SEQ ID NO:1). According to an embodiment of the present i nvention, when two or more copies of MAR sequences are contained in the 3' terminal r egion of the transcription terminator, these two or more copies of MAR sequences may be connected adjacently to each other, or may be separated by a relatively short spacer region. For example, the two or more copies of MAR sequences may be connected s equentially and adjacently to each other. In addition, according to an embodiment oft he present invention, the term "3" terminal of transcription terminator" refers to the 3' ter minal of a transcription terminator, or in other words, a polyadenylation (polyA) signal. However, the 3' terminal of a polyadenylation signal is not necessarily intended to mean the exact 3' terminal of the polyadenylation signal only, and should be interpreted to en compass the downstream region of the 3' terminal that is under the influence of the poly adenylation signal.
An example of the expression vector according to an embodiment of the present invention is an expression vector having any one of the nucleotide sequences of SEQ I D NOs: 1,2,5,6 and 7, or a pCMVMM-IgG expression vector having the vector map sh own in FIG. 14. A vector having the sequence of SEQ ID NOs: 1, 2, 6 or 7 is such that the polynucleotide encoding foreign product is a gene encoding lacZ, while a vector ha ving the sequence of SEQ ID NO:5 is such that the polynucleotide encoding foreign pro duct is a gene encoding GCSF. The pCMVMM-IgG expression vector having the vect or map shown in FIG. 14 is such that the polynucleotide encoding foreign product is a g ene encoding an immunoglobulin heavy chain and light chain.
According to another aspect of the present invention, there is provided a method of expressing a foreign gene, comprising culturing an animal cell that is transfected with an expression vector according to an embodiment of the present invention.
In the method according to the present invention, the animal cell may be any ani mal cell, and examples thereof include cells selected from the group consisting of CHO, BHK, NSO and human cells, but are not limited thereto. The animal cell may be a CH O cell. In addition, the method of culturing the animal cell may be any method that is k nown in the related art. A person having ordinary knowledge in the art would be able t o appropriately select the culturing conditions such as medium, temperature, etc., in ac cordance with the selected cell line.

ADVANTAGEOUS EFFECTS
The expression vector for an animal cell according to the present invention can b e used to significantly increase expression of foreign genes in animal cells.
The gene expression method according to the present invention can be used to express genes in animal cells easily with high efficiency.
MODE OF THE INVENTION Hereinafter, the present invention will be described in more detail with reference t
0 examples. However, these examples are provided only for the purpose of illustrating
the present invention and are not intended to limit the scope of the present invention.
EXAMPLES
The inventors of the present invention examined the effect of a MAR element tha t is contained in an expression vector for an animal cell and is attached to the 3' termina
1 of a transcription terminator of a gene, on the expression of the gene. To this end, fir
st, a vector having one or two copies of human p-globin MAR sequences inserted at a d
ownstream position of a SV40 polyadenylation signal was prepared. The prepared vec
tor was introduced into animal cells, and the animal cells were cultured in order to obser
ve the extent of expression of the gene.
EXAMPLE 1: Preparation of vector containing MAR sequence at the 3' terminal o fgene.
1. Isolation of human p-globin 5' MAR.
First, HepG-2 cells were cultured, and genome DNA was isolated from the obtain ed HepG-2 cells using DNeasy Kit (Qiagen, US), according to the instruction provided b y the manufacturer.
Subsequently, a polymerase chain reaction (PCR) was performed using the obtai ned genome DNA as a template, and using the oligonucleotides of SEQ ID NOs: 3 and 4 as primer, in order to amplify the 5' MAR sequence of human p-globin gene. PCR w as performed under the conditions of 35 cycles of 15 minutes at 94°C, 1 minute at 94°C 1 minute at 62°C and 3 minutes at 72°C, and another cycle of 10 minutes at 72°C.

The PCR product thus obtained was inserted into a yT&A cloning vector (Yeaster n Biotech Co., Ltd., Taiwan) to prepare a yT&A/ß-globin MAR vector having the 5' MAR sequence of ß-globin gene inserted therein. The yT&A cloning vector is a TA cloning v ector designed to allow direct cloning of a PCR product without using a restriction enzy me.
2. Preparation of expression vector for animal cell containing MAR sequence at t he 3' terminal of transcription terminator of a gene.
1) Preparation of pSVM-ß-gal and pSVMM-p-gal vectors, both having SV40 early promoter. lacZ gene and SV40 transcription terminator operablv connected thereto an d having one copy and two copies, respectively, of human ß-globin MAR sequences co nnected to the 3' terminal of SV40 transcription terminator.
Using a pSV-ß-gal vector (Promega, US) containing a SV40 early promoter and a lacZ gene operably connected to the promoter (See FIG. 1), an expression vector for an animal cell containing a MAR sequence at the 3' terminal of transcription terminator of a gene was prepared.
First, the yT&A/ß-globin MAR vector obtained in Section 1 was treated with Bam HI and Xbal, the product obtained from the treatment was isolated by agarose gel electr ophoresis, and BamHI-Xbal product was isolated from the product obtained from the tre atment. Next, the BamHI-Xbal product was ligated to a pSV-p-gal vector (Promega, U S) that had been treated with BamHI and Xbal, and thus a pSVM-p-gal vector having o ne copy of human p-globin MAR sequence connected to the 3' terminal of the SV40 tra nscription terminator (See FIG. 2) was obtained. The nucleotide sequence of the pSV M-p-gal vector was the same as the sequence of SEQ ID NO: 1.
Subsequently, the yT&A/p-globin MAR vector obtained in the above Section 1 w as treated with Xbal and Pstl, the product obtained from the treatment was isolated by agarose gel electrophoresis, and Xbal and Pstl product was isolated from the product o btained from the treatment. Next, the Xbal-Pstl product was ligated to a pSVM-p-gal v ector that had been treated with Xbal and Pstl, and thus a pSVMM-p-gal vector having t wo copies of human p-globin MAR sequences connected to the 3' terminal of the SV40 transcription terminator (See FIG. 3) was obtained. The nucleotide sequence of the p SVMM-p-gal vector was the same as the sequence of SEQ ID NO: 2.

2) Preparation of pCMVMM-ß-qal vector having CMV promoter. lacZ gene and S V40 transcription terminator operablv connected thereto, and having two copies of hum an p-globin MAR sequences connected to the 3' terminal of SV40 transcription terminat or.
Using a pCMV-ß-gal vector containing CMV promoter, lacZ gene and SV40 trans cription terminator operably connected thereto, an expression vector for an animal cell c ontaining two copies of human p-globin MAR sequence at the 3' terminal of transcriptio n terminator of a gene was prepared.
First, in order to insert two copies of human p-globin MAR sequences into the pC MV-p-gal vector containing CMV early promoter, lacZ gene and transcription terminator, the pCMV-p-gal vector was treated with Pmel to open the vector, and then the opened pCMV-p-gal vector was isolated and purified using agarose gel electrophoresis. Sub sequently, the opened pCMV-p-gal vector was treated with alkaline phosphatase to rem ove phosphate. After the removal of phosphate, the treatment product was heated at 65°C for 15 minutes to deactivate the alkaline phosphatase, which was then removed b y column chromatography. A pSVMM-p-gal vector was used to insert two copies of hu man p-globin MAR sequences into the opened pCMV-p-gal vector that had been treate d as described above. The pSVMM-p-gal vector was first treated with EcoRV to obtain a fragment of 5.8 kb containing two copies of human p-globin MAR sequences, and th e fragment was isolated and purified using agarose gel electrophoresis. Subsequently , the fragment containing two copies of MAR was inserted into the opened pCMV-p-gal vector with Pmel treatment. Thus, a complete pCMVMM-p-gal expression vector was obtained.
FIG. 8 is a diagram illustrating the pCMV-p-gal vector, which contains CMV-deriv ed promoter, lacZ gene and SV40 transcription terminator operably connected thereto, while FIG. 9 is a diagram illustrating the pCMVMM-p-gal vector, in which two copies of h uman ß-globin MAR sequences are sequentially connected to the 3' terminal of the SV4 0 transcription terminator located downstream of the lacZ gene of the pCMV-p-gal vecto r.
3) Preparation of pCMVMM-lqG vector having CMV promoter, immunoqlobulin q ene and SV40 transcrition terminator operablv connected thereto, and having two copi

es of human ß-globin MAR sequences connected to the 3' terminal of SV40 transcriptio n terminator.
Using a pCMV-IgG vector containing CMV promoter, human immunoglobulin G g ene and SV40 transcription terminator operably connected thereto, an expression vecto r for animal cell containing two copies of human p-globin MAR sequence at the 3' termi nal of the transcription terminator of IgG gene was prepared.
First, the pCMV-IgG vector was treated with Pmel to open the vector, and the op ened pCMV-IgG vector was isolated and purified by agarose gel electrophoresis. Next , the opened pCMV-IgG vector was treated with alkaline phosphatase to remove phosp hate. After the removal of phosphate, the treatment product was heated at 65°C for 1 5 minutes to deactivate the alkaline phosphatase, which was then removed by column c hromatography. A pSVMM-p-gal vector was used to insert two copies of human p-glo bin MAR sequences into the opened pCMV-IgG vector which had been treated as descr ibed above. The pSVMM-ß-gal vector was treated with EcoRV to obtain a fragment of 5.8 kb containing two copies of human p-globin MAR sequences, and the fragment was isolated and purified using agarose gel electrophoresis. Subsequently, the fragment containing two copies of MAR was inserted into the opened pCMV-IgG vector with Pme I treatment. Thus, a complete pCMVMM-IgG expression vector was obtained.
FIG. 13 is a diagram illustrating the pCMV-IgG vector, which contains CMV-deriv ed promoter and human immunoglobulin G gene operably connected to the promoter. The pCMV-IgG vector contains dhfr (dihydrofolate reductase) gene as a selective gen e. In Fig. 13, IS stands for intronic sequence.
FIG. 14 is a diagram illustrating the pCMVMM-IgG vector, in which two copies of human p-globin MAR sequences are sequentially connected to the 3' terminal of transcr iption terminator of the IgG gene (for heavy chain, BGH polyA; for light chain, SV40 pol yA) of the pCMV-IgG vector. The pCMVMM-IgG vector contains dhfr gene as a select! ve gene. In FIG. 14, IS stands for intronic sequence.
EXAMPLE 2: Effect of MAR sequence attached to the 3' terminal of gene on the expression of the gene.
In this example, the pSVM-ß-gal vector, pSVMM-ß-gal vector, pCMVMM-ß-gal ve ctor and pCMVMM-IgG vector prepared in Example 1 were introduced into animal cells,

and the animal cells were cultured in order to examine the effect of the human p-globi n MAR sequence attached to the 3' terminal of a gene on the expression of the gene. For the control, pSV-ß-gal vector (Promega, US), pCMV-p-gal vector and pCMV-lg vect or were used.
1. Transfection of CHO cell.
(1) Transfection using DOSPER (surfactant).
2 ng each of the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector were respectively co-transfected with 33 ng of pSV2neo vector (Clontech, US) into CH 0 DG44 cell lines (5x105 cells/well) using a surfactant DOSPER (Roche, Germany), acc ording to the instruction of the manufacturer. In order to perform the co-transfection, t he CHO DG44 cell lines were first washed once with a MEM-a medium containing nucl eoside but no serum, and then the cell lines were cultured in the same MEM-α medium. After 1 hour, the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector were respectively mixed with the pSV2neo vector containing a selective gene, and then with 5.3 |j,g of DOSPER (Roche, Germany). Then, the mixtures were allowed to react at a mbient temperature for 30 minutes. After the reaction of 30 minutes, the CHO DG44 c ell lines that had been cultured in the MEM-a medium were treated with the reaction mi xtures, respectively, and the treated cell lines were cultured together with the reaction m ixtures for 8 hours. Subsequently, the culture fluid was exchanged with an MEM-a me dium containing 10% (v/v) of heat-treated FBS and nucleoside, and the culture was con tinued for another 36 hours. The transfected CHO DG44 cells were cultured again in a selective medium containing G418 (a MEM-a medium containing 10% of heat-treated FBS, 850 jag/ml of G418 and nucleoside) for about 3 weeks, and the cell line having res istance to G418 was selected.
The obtained cell lines, that is, the cell lines transfected with the pSV-p-gal vecto r, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, and having resistance to G 418 were assayed, in order to examine the frequency of cells expressing p-galactosidas e and the amount of expressed p-galactosidase.
(2) Transfection using calcium phosphate.
2 μg each of the pSV-p-gal vector, pSVMM-p-gal vector, pCMV-p-gal vector and pCMVMM-ß-gal vector were respectively co-transfected with 500 ng of pSV2neo vector (Clontech, US) into CHO DG44 cell lines (5x105 cells/well) using calcium phosphate. I

n order to perform the co-transfection, the CHO DG44 cell lines were first washed once with a MEM-α medium containing nucleoside and 1% of FBS, and then the cell lines we re cultured in the same MEM-a medium. After 1 hour, the pSV-p-gal vector, pSVMM-p -gal vector, pCMV-p-gal vector and pCMVMM-p-gal vector were respectively mixed with
the pSV2neo vector containing a selective gene, and then with calcium phosphate to f orm precipitates. The CHO DG44 cell lines that had been cultured in the MEM-α medi um were treated with the previously formed precipitates for 4 hours, and then with a 10 % glycerol solution. After the 1-minute treatment, the glycerol solution was completely removed, subsequently the culture fluid was exchanged with an MEM-a medium contai ning 10% (v/v) of heat-treated FBS and nucleoside, and the culture was continued for a nother 36 hours. The transfected CHO DG44 cells were cultured again in a selective medium containing G418 (a MEM-α medium containing 10% heat-inactivated FBS, 850
tag/ml of G418 and nucleoside) for about 3 weeks, and the cell line having resistance t o G418 was selected.
The obtained cell lines, that is, the cell lines transfected with the pSV-p-gal vecto r, pSVMM-p-gal vector, pCMV-p-gal vector and pCMVMM-p-gal vector, respectively, an d having resistance to G418 were assayed, in order to examine the frequency of cells e xpressing ß-galactosidase and the amount of expressed p-galactosidase.
In addition, 2.5μg of each of the pCMV-IgG vector and the pCMVMM-IgG vector were respectively introduced into CHO DG44 cell lines (5x105 cells/well) using calcium phosphate. In order to perform the introduction, the CHO DG44 cell lines were first wa shed once with a MEM-a medium containing nucleoside and 1% of FBS, and then the c ell lines were cultured in this MEM-a medium. After 1 hour, the pCMV-IgG vector and t he pCMVMM-IgG vector were respectively mixed with calcium phosphate to form precip itates. The CHO DG44 cell lines that had been cultured in the MEM-a medium were r espectively treated with the precipitates for 4 hours, and then with a 10% glycerol soluti on for 1 minute. After the treatment of 1 minute, the glycerol solution was completely r emoved, subsequently the culture fluid was exchanged with an MEM-a medium contain! ng 10% (v/v) of heat-treated FBS and nucleoside, and the culture was continued for an other 72 hours. After the 72-hour culture, the transfected CHO DG44 cells were cultur ed in a 6-well plate using a selective medium (SFM4CHO medium (Hyclone, US)) in whi

ch only a cell line containing dfhr gene can grow. Subsequently, the amounts of IgG e xpression in the transfected CHO DG44 cell lines were examined.
2. Investigation of amount of B-aalactosidase expression and the frequency of B-galactosidase positive cells in cell lines respectively transfected with pSVM-ß-gal vector and pSVMM-B-aal vector and having resistance to G418.
In transient CHO DG44 cells transfected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-ß-gal vector, respectively, the amounts of ß-galactosidase express! on were measured through an analysis of B-galactosidase enzyme activity. First, the c ell lines were transfected, and after 48 hours, the CHO DG44 cell lines transfected with the pSV-B-gal vector, pSVM-p-gal vector and pSVMM-p-gal vector, respectively, were w ashed twice with 1X PBS, and the cells were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were washed twice with PBS, and then a I ysis buffer (0.25 M Tris-HCI containing 0.1% of Nonidet P40, pH 8.0) was added to the cells in an amount of 200 nl per 5x106 cells. The cell-buffer mixtures were allowed to r eact at 4°C for 30 minutes. During the reaction of 30 minutes, the cell-buffer mixtures were mixed using vortex every 10 minutes. After the reaction, the cell-buffer mixtures were centrifuged at 4°C at 13,000 rpm for 10 minutes, and then the supernatants were t ransferred to new tubes. The obtained supernatants, that is, the cell lysates, were sub jected to an analysis for ß-galactosidase enzyme activity using a ▬5-Gal assay kit (Invitro gen, US) according to the instructions of the manufacturer. 10 |o,l of each of the cell lys ates was added to a 96-well plate for EIA, and then 50 μl of a 1X cleavage solution (60 mM Na2HPO4-7H2O, 40 mM NaH2PO4-H20, 10 mM KCI, 1 mM MgSO47H20, pH 7.0) a nd 17 ul of an ONPG solution (concentration: 4 mg/ml) were added thereto, allowing the
mixture to react at 37°C for 30 minutes. 125μl of a reaction stop solution was added to terminate the reaction, and then the absorbance of the reaction mixture was measure d at 420 nm. The total amounts of protein in the cell lysates were measured according
to a bicinchoninic acid (BCA) method, and the p-galactosidase enzyme activities were normalized to the activity obtainable with a constant amount of protein for the analysis. FIG. 4 is a graph indicating analysis results of ▬5-galactosidase enzyme activity i n CHO DG44 cell lines in a transient state, which are transfected with the pSV-ß-gal vec tor, pSVM-ß-gal vector and pSVMM-ß-gal vector, respectively. As shown in FIG. 4, the

P-galactosidase expression did not increase in the case of transfection with one copy of MAR sequence as well as the case of transfection with two copies of MAR sequence s. It can be seen from the results that, as previously reported, the MAR element does not increase expression of a gene in a transiently transfected cell, even though the gen e is connected to the MAR element.
Subsequently, the ß-galactosidase enzyme activities in cell lines that were transf ected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector, respectiv ely, and had resistance to G418, were analyzed. First, 2 μg of the pSV-ß-gal vector, ß SVM-▬5-gal vector and pSVMM-p-gal vector were co-transfected with 33 ng of a pSV2ne o vector (Clontech, US) into CHO DG44 cell lines (5x105 cells/well) using a surfactant, DOSPER (Roche, Germany), according to the instructions of the manufacturer. After 36 hours of the co-transfection, the cell lines were cultured in a selective medium contai ning G418 (a MEM-α medium containing 10% of heat-treated FBS, 850 αag/ml of G418 and nucleoside) for about 3 weeks to obtain CHO DG44 cell lines having resistance to G418. The amounts of ß-galactosidase expression were measured in the CHO DG44 cell lines having resistance to G418 through analysis of p-galactosidase enzyme activity
FIG. 5 is a graph indicating analysis results of p-galactosidase enzyme activity in CHO DG44 cell lines that were transfected with pSV-ß-gal vector, pSVM-ß-gal vector an d pSVMM-ß-gal vector, respectively, and had resistance to G418. As shown in FIG. 5,
the amount of p-galactosidase expression increased 18- to 29-fold compared with the control, in the CHO DG44 cell lines having resistance to G418, by introducing the MAR sequence to the 3' terminal of polyadenylation signal. In particular, when two copies of
MAR sequences were introduced, the increasing effect was enhanced by about 60% c ompared with the case where one copy of MAR sequence was introduced.
Then the frequency of ß-galactosidase positive cells in the previously obtained C HO DG44 cell lines that were transfected with the pSV-p-gal vector, pSVM-ß-gal vector and pSVMM-p-gal vector, respectively, and had resistance to G418, were measured usi ng a ß-gal staining method. First, the cells cultured in a 6-well plate using a selective medium (a MEM-α medium containing 10% of heat-treated FBS, 850 μg/ml of G418 an d nucleoside) were washed twice with 1X PBS and were separated from the culture ves
sel using a 0.25% trypsin solution. The separated cells were treated with the selective

medium to deactivate trypsin, subsequently centrifuged to remove trypsin and were was hed twice with 1X PBS. After the washing, the cells were treated with a fixing solution comprising 2% formaldehyde and 0.2% glutaraldehyde at 4°C for 10 minutes to fix the c ells and were washed twice with PBS. Then, the cells were stained with ONPG, which is coloration product obtained by treating X-Gal, a substrate for p-Gal enzyme. As a re suit of the staining, positive cells turned ß-gal vector, respectively, and having resistanc e to G418 were stained with ONPG. As shown in FIG. 6, the frequency of ß-galactosid ase positive cells increased, as the MAR sequence was introduced at the 3' terminal of transcription termination region, that is, polyadenylation signal of a gene. This implies that the MAR sequence introduced at the 3' terminal of the polyadenylation signal incre ases the expression of the gene upstream thereto. Also, as shown in FIG. 6, when tw o copies of MAR sequences were introduced, the frequency of p-galactosidase positive cells significantly increased (about 90%), compared with the case where one copy of M AR sequence was introduced (about 70%).
FIG. 7 is a graph indicating the amounts of ß-galactosidase expression presente d in FIG. 5, which were recalculated on the basis of the frequency of p-galactosidase po sitive cells. As shown in FIG. 7, the amount of ß-galactosidase expression per positive cell unit increased 7.4- to 8.9-fold compared with the control, as a result of introducing human ß-globin MAR sequence to the 3' terminal of the ß-galactosidase gene. In parti cular, the amount of ß-galactosidase expression increased by about 20% in the case of introducing two copies of MAR sequences, compared with the case of introducing only one copy of MAR sequence.
3. Investigation of the amount of B-qalactosidase expression and the frequency of ß-galactosidase positive cells in cell line having pCMVMM-ß-qal vector introduced and having resistance to G418.
First, the amounts of ß-galactosidase expression in the cell lines which were tran sfected with the pCMV-ß-gal vector and pCMVMM-p-gal vector, respectively, and had r esistance to G418, were measured through analysis forß-galactosidase enzyme activit y. First, the G418-resistant CHO DG44 cells that had been cultured in a selective med

ium for about 3 weeks after transfection with the pCMV-ß-gal vector and pCMVMM-ß-ga I vector, respectively were washed two times with 1X PBS, and the cells were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were was hed two times with PBS, then 200μl of a lysis buffer (0.25 M Tris-HCI pH 8.0, 0.1% Non idet P40) was added per 106 cells, and the cell-buffer mixtures were allowed to react at 4°C for 30 minutes. During the reaction time of 30 minutes, the cell-buffer mixtures we re mixed using vortex every 10 minutes. After the reaction, the reaction mixtures were centrifuged at 4°C and at 13,000 rpm for 10 minutes, and the supernatants were transfe rred to new tubes. The obtained supernatants, that is, the cell lysates, were then subj ected to analysis for (3-galactosidase enzyme activity using a ß-Gal assay kit (Invitrogen , US), according to the instructions of the manufacturer. 10 μl of each of the cell lysate s was added to a 96-well plate for El A, and then 50 ^l of a 1X cleavage solution (60 mM Na2HP04-7H2O, 40 mM NaH2P04-H2O, 10 mM KCI, 1 mM MgSO4-7H2O, pH 7.0) and 17 μl of an ONPG solution (concentration: 4 mg/ml) were added thereto, allowing the mi xture to react at 37°C for 30 minutes. 125 μl of a reaction stop solution was added to ter minate the reaction, and then the absorbance of the reaction mixture was measured at 420 nm. The total amount of protein in the cell lysates was measured according to the bicinchoninic acid (BCA) method, and the p-galactosidase enzyme activity was normali zed to the activity obtainable with a constant amount of protein for the analysis.
FIG. 10 is a graph indicating analysis results of p-galactosidase enzyme activity i n the CHO DG44 cell lines that were transfected with the pCMV-p-gal vector and pCMV MM-p-gal vector, respectively, and had resistance to G418. As shown in FIG. 10, the amounts of p-galactosidase expression, which was connected to the CMV-derived prom oter, in the CHO DG44 cell lines having resistance to G418 increased about 6.3-fold co mpared with the control vector, as two copies of MAR sequences were introduced at th e 3' terminal of the polyadenylation signal.
Next, the frequency of ß-galactosidase positive cells was investigated using the ß -gal staining method. First, cells cultured in a 6-well plate using a selective medium (a MEM-α medium containing 10% of heat-treated FBS, 850 μg/ml of G418 and nucleosid e) were washed twice with 1X PBS and were separated from the culture vessel using a 0.25% trypsin solution. The separated cells were treated with the selective medium to deactivate trypsin, subsequently centrifuged to remove trypsin, and then washed twice

with 1X PBS. After the washing, the cells were treated with a fixing solution comprisin g 2% formaldehyde and 0.2% glutaraldehyde at 4°C for 10 minutes to fix the cells and were washed twice with PBS. Then the cells were stained with ONPG, which is a color ation product obtained by treating X-Gal, a substrate for ß-Gal enzyme. As a result of t he staining, the positive cells turned blue.
FIG. 11 is a graph indicating the frequency of ß-galactosidase positive cells, whic h were obtained as a result of staining the CHO DG44 cell lines, that were transfected with the pCMV-ß-gal vector and the pCMVMM-ß-gal vector, respectively, and had resist ance to G418, with ONPG. As shown in FIG. 11, the frequency of ß-galactosidase pos itive cells increased about 3.1-fold as MAR sequences were introduced at the 3' termina I of the transcription termination region, that is, the polyadenylation signal, of the gene. This implies that the MAR sequence introduced at the 3' terminal of the polyadenylatio n signal increased the gene expression, even in the case where the gene located upstr earn to the MAR sequence uses a CMV-derived promoter instead of SV40 promoter.
FIG. 12 is a graph indicating amounts of ß-galactosidase expression presented i n FIG. 10, which were recalculated on the basis of the frequency of p-galactosidase pos itive cells. As shown in FIG. 12, the amounts of p-galactosidase expression per positiv e cell unit increased about 2.2-fold compared with the control, when human ß-globin M AR sequence is introduced at the 3' terminal of gene.
4. Investigation of the amount of IgG expression in cell line having pCMVMM-IgG vector introduced and cultured in a medium for screening dhfr gene
CHO DG44 cells were transfected with the pCMV-IgG vector and the pCMVMM-l gG vector, respectively, and then the transfected CHO cells were cultured in a selective medium (SFM4CHO medium (Hyclone, US) containing 5% heat-inactivated and dialyz ed FBS) in which only those cell lines containing dhfr gene can grow, for 2 weeks. Su bsequently, these cell lines were inoculated onto a 6-well plate using 3 types of selectiv e media containing MTX at a concentration of 7x105 cells/ml, cultured for 3 days, and th en the amount of IgG expression in the culture fluid was measured. The selective med ia used contained 0 nM, 25 nM, 50 nM and 100 nM of MTX, respectively.
FIG. 15 is a graph indicating amounts of IgG expression measured after transfec ting CHO DG44 cell lines with the pCMVMM-IgG expression vector according to an em bodiment of the present invention and a control vector pCMV-IgG expression vector, re

spectively, and then inducing gene amplification by adding MIX to the transfected cell li nes. As shown in FIG. 15, the amount of IgG expression increased, as two copies of MAR sequences were introduced at the 3' terminal of the polyadenylation signal. Furl her, as the concentration of MIX increased, the rate of increase in the amount of IgG e xpression was higher for the pCMVMM-IgG expression vector compared with the contra I pCMV-IgG vector. When treated with 100 nM of MIX, the amount of IgG expression in the cells containing the pCMVMM-IgG vector increased about 6-fold, compared with t he cells containing the control pCMV-IgG vector.
FIG. 16 is a graph indicating results of comparison of the amounts of IgG expres sion in the culture fluid obtained in the experiment of FIG. 15, which were normalized to the expression amount values produced by 106 cells for 24 hours. As shown in FIG. 16, in the case of the pCMVMM-IgG vector, when the cells were treated with 100 nM of MITX, the amount of IgG expression increased about 5-fold, compared with the cell line containing the control pCMV-IgG vector. It can be also seen from FIG. 16 that as the MIX concentration is increased, the rate of increase in the amount of IgG expression al so increased. This implies that during the process of gene amplification, cells containi ng the pCMVMM-IgG vector are amplified and express the IgG gene more efficiently th an the cells containing the pCMV-IgG vector.
From the results of the Examples of the present invention as described above, it can be seen that when a human p-globin MAR sequence is introduced at the 3' terminal of a transcription termination signal of a gene, expression of an upstream gene located next to a promoter including SV40 promoter and CMV promoter is significantly enhanc ed. Introduction of one copy of a human p-globin MAR sequence led to a significant in crease in the expression of the upstream gene, and in particular, introduction of two cop ies of human p-globin MAR sequences led to further enhancement in the increasing eff ect induced by the introduction of one copy of the MAR sequence. This occurrence is believed to be caused by the notable reduction of the position effects by the introduced MAR sequence on adjacent nucleic acid sequences present in the host cell, but the pre sent invention is not intended to be limited to this specific mechanism.

INDUSTRIAL APPLICABILITY
The expression vector for an animal cell according to an embodiment of the pres ent invention can be used to significantly increase expression of foreign genes in anima I cells.
The gene expression method according to an embodiment of the present invent! on can be used to express genes in animal cells easily with high efficiency.

-CLAIMS-
1.
An expression vector for an animal cell comprising a promoter, a cloning site or a polynucleotide encoding foreign product, and a transcription terminator, all of which ar e operably connected each other within the expression vector, wherein at least one cop y of human p-globin matrix attachment region (MAR) is located at the 3' terminal of the t ranscription terminator.
2.
The expression vector of claim 1, wherein the promoter is SV40 early promoter o r CMV promoter.
3.
The expression vector of claim 1, wherein the polynucleotide encoding the foreig n product is a gene encoding lacZ, immunoglobulin, GCSF or EPO.
4.
The expression vector of claim 1, wherein the transcription terminator is SV40 vir us transcription terminator.
5.
The expression vector of claim 1, wherein the MAR sequence is the sequence of Genbank Accession No. L22754.
6.
The expression vector of claim 1, comprising a polynucleotide containing nucleoti des 4161 to 10134 of SEQ ID N0:2, in which two copies of human p-globulin MAR seq uences are connected adjacently to each other.
7.
The expression vector of claim 1, wherein two or more copies of human p-globin MAR sequences are linked to the 3' terminal of the transcription terminator, and the MA

R sequences are connected adjacently to each other, or are separated by a coding seq uence or a non-coding sequence.
8.
The expression vector of claim 1, having any one of the nucleotide sequences S EQ ID NOs: 1, 2, 5, 6 and 7, or a pCMVMM-IgG expression vector having the vector ma p shown in FIG 14.
9.
A method of expressing a foreign gene, comprising an animal cell transfecting wi th the expression vector according to any one of claims 1 to 8, which comprises a polyn ucleotide encoding the foreign protein, and culturing the transfected animal cell.
10.
The method of claim 9, wherein the animal cell is selected from the group consist ing of CHO, BHK, NSO and human cells.
11.
An expression vector and a method of expressing a foreign gene substantially such as herein described with reference to the accompanying drawings and as illustrated in foregoing examples.

Documents:

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Patent Number

271186

Indian Patent Application Number

7058/DELNP/2007

PG Journal Number

07/2016

Publication Date

12-Feb-2016

Grant Date

08-Feb-2016

Date of Filing

12-Sep-2007

Name of Patentee

CELLTRION, INC.

Applicant Address

13-6 SONGDO-DONG, YEONSU-GU, INCHEON-CITY 406-130 REPUBLIC OF KOREA

Inventors:

#	Inventor's Name	Inventor's Address
1	KIM, JONG-MOOK	117-206 HYUNDAI 1CHA APT., DONGCHUN-DONG, YEONSU-GU, INCHEON-CITY 406-130, REPUBLIC OF KOREA
2	HONG, HYE-JIN	RM.810 IRIUM3 OFFICETEL 599-1 YEONSU2-DONG, YEONSU-GU, INCHEON-CITY 406-818 REPUBLIC OF KOREA
3	LEE, HYUN-JOO	102-307 SAMHWAN APT., MANSU 1-DONG, NAMDONG-GU, INCHEON-CITY 405-740 REPUBLIC OF KOREA
4	SO, MOON-KYOUNG	1843-607 BANDALMAEUL APT., SANG 1-DONG, WONMI-GU, BUCHEON-CITY 420-751 REPUBLIC OF KOREA
5	LEE, SOO-YOUNG	103-502 KYUNGNAM APT., YEONSU3-DONG, YEONSU-GU, INCHEON-CITY 406-710 REPUBLIC OF KOREA
6	CHO, JONG-MOON	GA-406 KUKYOUNG APT., JUAN2-DONG, NAM-GU, INCHEON-CITY 402-844 REPUBLIC OF KOREA
7	CHUN, BOK-HWAN	725-1501 HYUNDAI APT., SALGUGOL, YOUNGTONG-DONG, YOUNGTONG-GU, SUWON-CITY, KYUNGKI-DO 443-736, REPUBLIC OF KOREA
8	HONG, SEOUNG-SUH	109-404 CHEONGGU APT., JEONMIN-DONG, YUSEONG-GU, DAEJEON-CITY 305-729 REPUBLIC OF KOREA
9	CHO, MYUNG-SAM	105-401 DAEWOO 3CHA APT., 920-1 DONGCHUN-DONG, YEONSU-GU, INCHEON-CITY 406-776 REPUBLIC OF KOREA

PCT International Classification Number

C12N 15/85

PCT International Application Number

PCT/KR2006/000753

PCT International Filing date

2006-03-04

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-2005-0018130	2005-03-04	Republic of Korea