Transcriptional Pause Release Is a Rate-Limiting Step for Somatic Cell Reprogramming

Abstract

Reactivation of the pluripotency network during somatic cell reprogramming by exogenous transcription factors involves chromatin remodeling and the recruitment of RNA polymerase II (Pol II) to target loci. Here, we report that Pol II is engaged at pluripotency promoters in reprogramming but remains paused and inefficiently released. We also show that bromodomain-containing protein 4 (BRD4) stimulates productive transcriptional elongation of pluripotency genes by dissociating the pause release factor P-TEFb from an inactive complex containing HEXIM1. Consequently, BRD4 overexpression enhances reprogramming efficiency and HEXIM1 suppresses it, whereas Brd4 and Hexim1 knockdown do the opposite. We further demonstrate that the reprogramming factor KLF4 helps recruit P-TEFb to pluripotency promoters. Our work thus provides a mechanism for explaining the reactivation of pluripotency genes in reprogramming and unveils an unanticipated role for KLF4 in transcriptional pause release.

Capturing the interactome of newly transcribed RNA

“…2d). For assessing ppRNAs, we divided genes in transcriptionally paused or not paused based on the RNA polymerase II (Pol II) traveling ratio (TR) 9,14 (Supplementary Fig. 3a) using a previously reported data set 15 .…”

Neonatal expression of RNA-binding protein IGF2BP3 regulates the human fetal-adult megakaryocyte transition

“…In addition, a factor or factors in the BET family have been shown to participate in pluripotency reprogramming of somatic cells (41), suggesting potential BET regulation of IGF2BP3. For these reasons, effects of BET inhibition on neonatal megakaryopoiesis were tested.…”

Ready, pause, go: regulation of RNA polymerase II pausing and release by cellular signaling pathways

“…Pol II is engaged but paused at the promoters of several pluripotency genes during reprograming [85]. The release of paused Pol II requires BRD4-dependent release of P-TEFb from the 7SK-HEXIM complex, followed by P-TEFb recruitment to pluripotency promoters by the reprogramming factor KLF4.…”