DEVELOPMENT OF ANIMAL CELL EXPRESSION SYSTEM WHICH CONFERS POSITION-INDEPENDENT AND ENHANCED FOREIGN GENE EXPRESSION

In order to develop the novel gene expression system, we introduced new control elements which could influence the foreign gene expression in animal cells. When the foreign genes are introduced into the genome of higher eukaryotic cells, the expressions from these integrated genes are often low and can vary greatly depending on the positions of the integration sites due to the complex nature of the chromatin structures (1). First we screened the various DNA sequence elements which can function as an insulator of gene expression from these position effects and can cooperate with the SV40 enhancer/promoter. Among the several DNA elements from the various sources, we identified the particular DNA element which confers the increased frequency of the positive colonies, assayed by the reporter gene from stable selections indicating significantly reduced position effects. This element also showed the several fold-increased expression level as well as the copy-number dependent expression with host cell specificity. Second we modified the transcription termination element where we introduced the specific terminator in combination with SV40 polyA signal. This modified terminator showed the increased efficiency and the level of the gene expression. By combining these two elements, we made the animal cell expression system and tested successfully for the recombinant protein productions of TGF ${\beta}$-soluble receptor, Antithrombin III, and single chain Pro-Urokinase. [Supported by grants from MOCIE]