Pluripotency Transcription Factor Oct4 Mediates Stepwise Nucleosome Demethylation and Depletion

Abstract

The mechanisms whereby the crucial pluripotency transcription factor Oct4 regulates target gene expression are incompletely understood. Using an assay system based on partially differentiated embryonic stem cells, we show that Oct4 opposes the accumulation of local {H3K9me2} and subsequent Dnmt3a-mediated {DNA} methylation. Upon binding {DNA,} Oct4 recruits the histone lysine demethylase Jmjd1c. Chromatin immunoprecipitation {(ChIP)} time course experiments identify a stepwise Oct4 mechanism involving Jmjd1c recruitment and {H3K9me2} demethylation, transient {FACT} (facilitates chromatin transactions) complex recruitment, and nucleosome depletion. Genome-wide and targeted {ChIP} confirms binding of newly synthesized Oct4, together with Jmjd1c and {FACT,} to the Pou5f1 enhancer and a small number of other Oct4 targets, including the Nanog promoter. Histone demethylation is required for both {FACT} recruitment and H3 depletion. Jmjd1c is required to induce endogenous Oct4 expression and fully reprogram fibroblasts to pluripotency, indicating that the assay system identifies functional Oct4 cofactors. These findings indicate that Oct4 sequentially recruits activities that catalyze histone demethylation and depletion.