Oct4 redox sensitivity potentiates reprogramming and differentiation
The transcription factor Oct4/Pou5f1 is a key component of the regulatory circuitry governing pluripotency. Oct4 is also widely used to generate induced pluripotent stem cells (iPSCs) from somatic cells. These observations provide compelling rationale to understand Oct4's functions. Here we used domain swapping and mutagenesis to compare Oct4's reprogramming activity with the paralog Oct1/Pou2f1, identifying a redox-sensitive DNA binding domain cysteine residue (Cys48) as a key determinant of both reprogramming and differentiation. In combination with the Oct4 N-terminus, mutating Oct1's serine at this position to cysteine is sufficient to confer strong reprogramming activity. Conversely, Oct4C48S strongly reduces reprogramming potential. Oct4C48S renders the protein insensitive to oxidative inhibition of DNA binding. The same mutation prevents oxidation-mediated protein ubiquitylation. An engineered Pou5f1C48S point mutation has little effect on undifferentiated cells embryonic stem cells (ESCs), but upon retinoic acid (RA)-mediated differentiation causes retention of Oct4 expression, decreased proliferation, and increased apoptosis. Transcriptional profiling reveals that the retention of pluripotency also manifests at the RNA level. Pou5f1C48S ESCs also contribute poorly to adult somatic tissues and form less differentiated teratomas. Collectively, the data support a model in which Oct4 redox sensing is a positive reprogramming determinant during one or more reprogramming steps, and mediates Oct4 degradation during differentiation. Overall design: To investigate the gene expression difference and similarity in parent and Oct4 C48S mutant Bl/6J ESC in pluripotent state as well as RA differentiation state, we extracted RNA from each cell line of two states for sequencing