Recombinant erythropoietin expression elevates by ubiquitous chromatin opening element (UCOE) in CHO DG44 cells

The growing demand for biopharmaceuticals has increased the need for efficient and cost-effective recombinant protein production platforms. Transcriptional gene silencing after random genomic integration of expression vectors remains a major limitation in mammalian expression systems and often reduces protein yield. Incorporation of ubiquitous chromatin opening elements (UCOEs) into expression cassettes has emerged as a promising strategy to mitigate position effects and enhance transgene expression. This study examined the effect of a UCOE-containing expression system on erythropoietin (EPO) production in Chinese hamster ovary (CHO) DG44 cells. A codon-optimized EPO expression cassette was introduced into CHO DG44 cells using either a conventional pOptiVEC vector and a UCOE-containing vector following random genomic integration. Recombinant EPO expression was assessed at the transcriptional and protein levels using reverse transcription quantitative polymerase chain reaction (RT-qPCR), western blotting, and enzyme-linked immunosorbent assay (ELISA). The UCOE-containing cell pool exhibited a significant enhancement in recombinant EPO expression, with approximately a 3.8-fold increase in mRNA levels and a sevenfold increase in secreted protein levels compared to the non-UCOE control cell pool. These results show that incorporating a UCOE reduces position-dependent gene silencing and increases recombinant mRNA and protein expression in CHO DG44 cell pools. This strategy supports improved efficiency during the early stages of cell line development for recombinant protein production.