Multiple P-TEFbs cooperatively regulate the release of promoter-proximally paused RNA polymerase II

Nucleic Acids Res. 2016 Aug 19;44(14):6853-67. doi: 10.1093/nar/gkw571. Epub 2016 Jun 28.


The association of DSIF and NELF with initiated RNA Polymerase II (Pol II) is the general mechanism for inducing promoter-proximal pausing of Pol II. However, it remains largely unclear how the paused Pol II is released in response to stimulation. Here, we show that the release of the paused Pol II is cooperatively regulated by multiple P-TEFbs which are recruited by bromodomain-containing protein Brd4 and super elongation complex (SEC) via different recruitment mechanisms. Upon stimulation, Brd4 recruits P-TEFb to Spt5/DSIF via a recruitment pathway consisting of Med1, Med23 and Tat-SF1, whereas SEC recruits P-TEFb to NELF-A and NELF-E via Paf1c and Med26, respectively. P-TEFb-mediated phosphorylation of Spt5, NELF-A and NELF-E results in the dissociation of NELF from Pol II, thereby transiting transcription from pausing to elongation. Additionally, we demonstrate that P-TEFb-mediated Ser2 phosphorylation of Pol II is dispensable for pause release. Therefore, our studies reveal a co-regulatory mechanism of Brd4 and SEC in modulating the transcriptional pause release by recruiting multiple P-TEFbs via a Mediator- and Paf1c-coordinated recruitment network.

MeSH terms

  • Acetamides / pharmacology
  • Cell Cycle Proteins
  • HCT116 Cells
  • HeLa Cells
  • Humans
  • Models, Biological
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Phosphorylation / drug effects
  • Positive Transcriptional Elongation Factor B / metabolism*
  • Promoter Regions, Genetic*
  • RNA Polymerase II / metabolism*
  • RNA, Small Interfering / metabolism
  • Transcription Elongation, Genetic / drug effects
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcriptional Elongation Factors / metabolism


  • Acetamides
  • BRD4 protein, human
  • Cell Cycle Proteins
  • NSMF protein, human
  • Nuclear Proteins
  • RNA, Small Interfering
  • SUPT5H protein, human
  • Transcription Factors
  • Transcriptional Elongation Factors
  • Positive Transcriptional Elongation Factor B
  • RNA Polymerase II
  • hexamethylene bisacetamide