Our proprietary expression module ‘SuRE12-EH’ enables high-level stable expression in CHO cells. In comparison to the CMV promoter, SuRE12-EH generates high protein expression in more cells (Figure A) enabling stable-pool approaches and facilitating the isolation of more stable clones with higher expression levels. The improved stability of the module is even more apparent when cells are taken off selection for 4 weeks (Figure B).
Figure legend. A. a stable cell pool driving YFP expression either under the CMV promoter or theSuRE12-EH module was generated by 3 weeks of selection under neomycin. Cells were then analysed for YFP expression by FACS. B. The cell pool of (A) was maintained for another 4 weeks without neomycin selection and again analysed for YFP expression.
The SuRE12-EH module is based on a screen for strong promoters and enhancers for which we generated a library containing >100 million random DNA elements of the CHO genome. This library effectively covers the CHO genome approximately 30 fold. Performing a SuRE screen with this library in CHO cells we identified many promising regulatory elements and by testing combinations of these for expression at the protein level we identfied SuRE12-EH.