Analysis of Protein Expression via Alternate 3’ Untranslated Region (UTR) Signals Through the Use of Site Specific Recombination

Chinese Hamster Ovary (CHO) cells remain the workhorse of the biopharmaceutical industry. We used site specific recombination in CHO cells to evaluate the post-translational effects of different poly-A signals. Recombinase (Flp) assisted generation of CHO pools show a significant difference in intra-clonal variation within in the pools. Moreover, the use of FRT/Flp resulted in an isogenic population which has allowed accurate correlation between mRNA levels and recombinant protein yields. We identified a human derived 3’UTR which generated a higher level of mRNA when compared to the more commonly used SV40 poly-A, the corresponding recombinant protein levels was found to be independent of the transcript levels.