RNA polymerase II–associated factor 1 regulates the release and phosphorylation of paused RNA polymerase II

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Science  11 Dec 2015:
Vol. 350, Issue 6266, pp. 1383-1386
DOI: 10.1126/science.aad2338

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“Please release me, let me go.”

RNA polymerase II (Pol II) is the principal protein complex required for gene transcription in metazoan cells. Many genes have a “paused” Pol II near their promoters, waiting to be released so they can start messenger RNA synthesis. Yu et al. show that Pol II–associated factor 1 (PAF1) plays a central role in regulating the activation of these paused Pol II complexes. The positive transcription elongation factor b helps recruit PAF1 to the paused Pol II. This facilitates the phosphorylation of Pol II on its C-terminal domain, freeing it to start transcription in earnest.

Science, this issue p. 1383


Release of promoter-proximal paused RNA polymerase II (Pol II) during early elongation is a critical step in transcriptional regulation in metazoan cells. Paused Pol II release is thought to require the kinase activity of cyclin-dependent kinase 9 (CDK9) for the phosphorylation of DRB sensitivity–inducing factor, negative elongation factor, and C-terminal domain (CTD) serine-2 of Pol II. We found that Pol II–associated factor 1 (PAF1) is a critical regulator of paused Pol II release, that positive transcription elongation factor b (P-TEFb) directly regulates the initial recruitment of PAF1 complex (PAF1C) to genes, and that the subsequent recruitment of CDK12 is dependent on PAF1C. These findings reveal cooperativity among P-TEFb, PAF1C, and CDK12 in pausing release and Pol II CTD phosphorylation.

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