Evaluating post-transcriptional regulatory elements for enhancing transient gene expression levels in CHO K1 and HEK293 cells

Five post-transcriptional regulatory elements, (i) the 5′ untranslated region (UTR) of human heat shock protein 70 mRNA (Hsp70), (ii) the 163-bp long splice variant derived from the 5′ UTR of vascular endothelial growth factor (SP163), and (iii) the tripartite leader sequence of human adenovirus mRNA linked with a major late promoter enhancer (TM), (iv) the first intron of human cytomegalovirus immediate early gene (Intron A), and (v) the post-transcriptional regulatory element derived from woodchuck hepatitis virus (WPRE), are evaluated for enhancing transient gene expression levels in two industrial cell lines, HEK293 and CHO K1 using firefly luciferase (Fluc), interferon γ (IFN), and Trastuzamab monoclonal antibody. Except for the Hsp70 which has no effects, all other elements enhance expression but exhibit cell-specific and gene-specific effects. TM provides the most universal and highest enhancement of gene expression levels. It enhances the expression of all three proteins in HEK293 cells and two proteins, Fluc and IFN in CHO K1 cells by 3.6- to 7.6-fold. The remaining elements enhance expression of one or more proteins in at least one cell line by 1.7- to 3.2-fold. Combining WPRE with either Intron A, SP163, or TM has cumulative effects on gene expression. The combinations can increase Fluc expression by up to 10.5-fold in HEK293 cells. These results provide valuable information to improve vectors for high level transient gene expressions in HEK293 and CHO K1 cells.