Improved yield of rhEPO in CHO cells with synthetic 5' UTR

The impact of local structure on mRNA translation is not well-defined pertaining to the 5' UTR. Reports suggest structural remodelling of the 5' UTR can significantly influence mRNA translation both in cis and trans however a new layer of complexity has been applied to this model with the now known reversible post-transcriptional chemical modification of RNA. N⁶-methyladenosine (m⁶A) is the most abundant internal base modification in mammalian mRNA. It has been reported that mRNAs harbouring m⁶A motifs in their 5' UTR have improved translation efficiency. The present study evaluated the addition of putative m⁶A motifs to the 5' UTR of a model recombinant human therapeutic glycoprotein, Erythropoietin (EPO), in a direct comparison with an A to T mutant and a no adenosine control. The m⁶A construct yielded significantly improved EPO titer in transient batch culture over no adenosine and m⁶T controls by 2.84 and 2.61-fold respectively. This study highlights that refinement of transgene RNA elements can yield significant improvements to protein titer.