Optimization of mammalian expression vector by cis-regulatory element combinations

Synthetic enhancers including TFREs improve transgene expression in CHO cells

“…Different strategies have been used to increase the productivity and quality of protein in CHO expression systems [ 7 , 10 , 13 , 16 ]. Expression vectors are one of key elements that influence recombinant protein yield and quality; thus, optimization of expression vectors can greatly increase transgene expression levels [ 13 , 16 , 17 , 21 ]. The promoter is the main component of the vector expression cassette, and optimization of promoter can improve targeting specificity and gene expression [ 34 , 35 ].…”

“…The strong human cytomegalovirus major immediate early gene (CMV) promoter is widely applied to express the GOI in CHO cell system. However, CMV promoter is inherently prone to silencing, leading to drop in yield during long-time expression [ [19] , [20] , [21] , [22] , [23] , [24] ]. The CMV promoter mainly consists of an upstream regulatory sequence (URS), CMV enhancer, core polymerase II promoter, first exon, and intron A [ 25 , 26 ].…”