Association of Cdk-activating kinase subunits with transcription factor TFIIH

Nature. 1995 Mar 16;374(6519):280-2. doi: 10.1038/374280a0.


The RNA polymerase II large subunit contains an essential carboxy-terminal domain (CTD) believed to be involved in the response to regulators during transcription initiation. The CTD is phosphorylated on a portion of RNA polymerase II molecules in vivo and it can be phosphorylated by the general transcription factor TFIIH in vitro. A highly purified TFIIH from rat liver has been described; this, like human and yeast TFIIH, contains associated CTD kinase and helicase activities. We report here that two polypeptides of the purified mammalian TFIIH are the MO15/Cdk7 kinase and cyclin H subunits of the Cdk-activating kinase Cak, previously identified as a positive regulator of Cdc2 and Cdk2. TFIIH and Cak preparations are each capable of phosphorylating recombinant CTD and recombinant Cdk2 proteins. The presence of Cak in TFIIH indicates that Cak may have roles in transcriptional regulation and in cell-cycle control.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • CDC2-CDC28 Kinases*
  • Cyclin H
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases / metabolism
  • Cyclins / metabolism
  • Enzyme Activation
  • Liver / metabolism
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Polymerase II / metabolism
  • Rats
  • Transcription Factor TFIIH
  • Transcription Factors / metabolism*
  • Transcription Factors, TFII*
  • Transcription, Genetic / physiology


  • CCNH protein, human
  • Ccnh protein, rat
  • Cyclin H
  • Cyclins
  • Transcription Factors
  • Transcription Factors, TFII
  • Transcription Factor TFIIH
  • Protein-Serine-Threonine Kinases
  • CDC2-CDC28 Kinases
  • Cdk2 protein, rat
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases
  • cyclin-dependent kinase-activating kinase
  • RNA Polymerase II