Recombinant Erythropoietin Expression Elevates by UCOE in CHO DG44 Cells

Abstract Purpose The demand for biopharmaceuticals has significantly increased in recent years. Achieving high-yield and cost-effective production of therapeutics remains a critical challenge. However, transcriptional gene silencing is a common issue in recombinant cell lines, often resulting in diminished protein expression levels. A promising strategy to overcome this challenge is the engineering of the expression cassette, particularly through the ubiquitous chromatin opening elements (UCOEs), unmethylated CpG island fragments derived from housekeeping genes. In this study, we utilized an expression platform incorporating a UCOE to enhance the expression of erythropoietin (EPO) in CHO DG44 cells.Methods The codon-optimized EPO sequence was cloned into the pOptiVEC vector, and subsequently, the EPO-IRES-DHFR fragment was inserted into the UCOE vector. Each linearized gene cassette was transfected into CHO DG44 cells. Subsequently, protein expression levels were assessed using quantitative Real-Time PCR, Western blotting, and enzyme-linked immunosorbent assay (ELISA).Results Our findings demonstrated a significant increase in EPO expression at both the mRNA and protein levels in the UCOE-EPO-IRES-DHFR pool, which were 3.8 and 7 times higher compared to pOptiVEC-EPO, respectively.Conclusion This study suggests that UCOE elements can mitigate insertion-site position effects and enhance recombinant mRNA and protein expression in CHO DG44 cell lines. Additionally, these elements can substantially reduce the time and cost associated with large-scale recombinant protein production.