Comparison of the effects of different combinations of expression regulatory elements on gene expression in mammalian cells

Background: At present, the function of numerous individual regulatory elements has been characterized extensively, but the combined effect of various cis-regulatory elements on gene expression in mammalian cells has been less discussed. Results In the present study, we examined the function of the combined effect of various cis-regulatory elements on gene expression in mammalian cells. To detect the function of different combinations of cis-acting elements on gene expression, we compared the effects of four promoters (PGK, Polr2a and EF-1α core promoter), two enhancers (CMV and SV40 enhancer), two introns (EF-1α intron A and hybrid intron), two terminators (CYC1 and TEF terminator) and their different combinations on gene expression. We constructed expression vectors with different combinations of these regulatory elements and detect the expression of eGFP by fluorescence intensity contrast and western blotting. Here we report that different combinations of cis-acting elements have a significant effect on protein expression. The vector with CMV enhancer, EF-1α core promoter and TEF terminator can express about three times higher eGFP than the unmodified vector in different animal cells. Conclusions We demonstrate that a direct combination of multiple regulatory elements capable of regulating gene expression did not exhibit synergistic effects. Our results show that regulation of protein expression can be achieved by optimizing the combination of cis-acting elements, and these findings can be used in biological applications that require regulation of gene expression.