Improved mammalian expression systems by manipulating transcriptional termination regions.

Here we show that the transcriptional terminator element of human gastrin gene, which is the only element characterized to date in terms of its function in transcriptional termination, increases the transient expression levels of recombinant proteins. The expression of the beta-galactosidase gene was enhanced 3-4-fold in HeLa cells by inserting the terminator element of human gastrin gene at the 3'-side of the SV40 polyadenylation signal/cleavage site of the control vector (pSV-beta-gal). This effect of the terminator element is orientation-dependent but not cell-specific since a similar enhancement of beta-galactosidase gene expression was detected in COS.M6 and CHO DG44 cells. The increased level of beta-galactosidase gene expression by the transcriptional terminator element of human gastrin gene turned out to arise from elevated cellular mRNA levels, suggesting that the terminator element stabilizes mRNA by enhancing proper 3'-end processing of mRNA.