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. 2015 Nov 25;1(2):106–116. doi: 10.1002/icl3.1037

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© 2015 The Authors. Inside the Cell published by WILEY Periodicals, Inc.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

PMC Copyright notice

The role of positive transcription elongation factor b (P‐TEFb) in a regulation of pol II transcription. P‐TEFb, comprising cyclin‐dependent kinase 9 (CDK9) and a cyclin T1 subunit, exists in a catalytically inactive small nuclear ribonucleic particle with 7SK snRNA and HEXIM1. Active P‐TEFb is bound instead to bromodomain‐containing protein 4 (Brd4) and stimulates elongation through phosphorylation of the pol II carboxyl‐terminal domain (CTD) on Ser2 and two negative transcription elongation factors: DRB sensitivity‐inducing factor (DSIF) and negative elongation factor (NELF). Phosphorylation converts DSIF from a repressor to an activator, whereas phosphorylated NELF leaves the elongation complex.