Cdk-activating kinase complex is a component of human transcription factor TFIIH

Nature. 1995 Mar 16;374(6519):283-7. doi: 10.1038/374283a0.


Transcription factor IIH (TFIIH) contains a kinase capable of phosphorylating the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II (RNAPII). Here we report the identification of the Cdk-activating kinase (Cak) complex (Cdk7 and cyclin H) as a component of TFIIH after extensive purification of TFIIH by chromatography. We find that affinity-purified antibodies directed against cyclin H inhibit TFIIH-dependent transcription and that both cyclin H and Cdk7 antibodies inhibit phosphorylation of the CTD of the largest subunit of the RNAPII in the preinitiation complex. Cak is present in at least two distinct complexes, TFIIH and a smaller complex that is unable to phosphorylate RNAPII in the preinitiation complex. Both Cak complexes, as well as recombinant Cak, phosphorylate a CTD peptide. Finally, TFIIH was shown to phosphorylate both Cdc2 and Cdk2, suggesting that there could be a link between transcription and the cell cycle machinery.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Chromatography, Affinity
  • Cyclin H
  • Cyclin-Dependent Kinases*
  • Cyclins / metabolism
  • Detergents
  • HeLa Cells
  • Humans
  • Immunologic Techniques
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / isolation & purification
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Polymerase II / metabolism
  • Recombinant Proteins / metabolism
  • Sarcosine / analogs & derivatives
  • Transcription Factor TFIIH
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*
  • Transcription Factors, TFII*
  • Transcription, Genetic


  • CCNH protein, human
  • Cyclin H
  • Cyclins
  • Detergents
  • Recombinant Proteins
  • Transcription Factors
  • Transcription Factors, TFII
  • Transcription Factor TFIIH
  • sarkosyl
  • Protein Kinases
  • carboxy-terminal domain kinase
  • Protein-Serine-Threonine Kinases
  • Cyclin-Dependent Kinases
  • cyclin-dependent kinase-activating kinase
  • RNA Polymerase II
  • Sarcosine