Npac Is a Co-factor of Histone H3K36me3 and Regulates Transcriptional Elongation in Mouse ES Cells

Chromatin modification contributes to pluripotency maintenance in embryonic stem cells (ESCs). However, the related mechanisms remain obscure. Here, we show that Npac, a "reader" of histone H3 lysine 36 trimethylation (H3K36me3), is required to maintain mouse ESC pluripotency since knockdown of Npac causes mouse ESC differentiation. Depletion of Npac in mouse embryonic fibroblasts (MEFs) inhibits reprogramming efficiency. Furthermore, our Npac ChIP-seq results reveal that Npac co-localizes with histone H3K36me3 in gene bodies of actively transcribed genes in mESCs. Interestingly, we find that Npac interacts with p-TEFb, RNA Pol II Ser2 and Ser5. Depletion of Npac disrupts transcriptional elongation of pluripotency genes Nanog and Rif1. Taken together, we propose that Npac is essential for transcriptional elongation of pluripotency genes by recruiting of p-TEFb and interacting with RNA Pol II Ser2 and Ser5.