Chromatin binding and regulation by Oct4 and artificially evolved POU (ePOU) in pluripotency reprogramming

We generated Oct4 libraries by randomizing selected amino acids and by recombining domains of paralogous POU family genes. These libraries were subjected to iterative rounds of pooled screens to select variants that enhance pluripotency induction. We identified an artificially evolved POU factor (ePOU) that substantially outperforms wild-type Oct4 in terms of mouse embryonic fibrobast (MEF) reprogramming. To probe whether the ePOU and Oct4 differentially engage the chromatin of reprogramming cells, we performed Assay for Transposase-Accessible Chromatin with highthroughput sequencing (ATACseq) for both factors and different combination. Two cocktails Sox2 (S), Klf4 (K), c-Myc (M) plus Oct4 (O) or ePOU(e) were transduced into OG2 MEF cells which is MEF cells with Oct4 promotor.