In vitro assembly of a functional human CDK7-cyclin H complex requires MAT1, a novel 36 kDa RING finger protein

EMBO J. 1995 Nov 15;14(22):5608-17.


It is proposed that the CDK7-cyclin H complex functions in cell cycle progression, basal transcription and DNA repair. Here we report that in vitro reconstitution of an active CDK7-cyclin H complex requires stoichiometric amounts of a novel 36 kDa assembly factor termed MAT1 (ménage à trois 1). Sequencing of MAT1 reveals a putative zinc binding motif (a C3HC4 RING finger) in the N-terminus; however, this domain is not required for ternary complex formation with CDK7-cyclin H. MAT1 is associated with nuclear CDK7-cyclin H at all stages of the cell cycle in vivo. Ternary complexes of CDK7, cyclin H and MAT1 display kinase activity towards substrates mimicking both the T-loop in CDKs and the C-terminal domain of RNA polymerase II, regardless of whether they are immunoprecipitated from HeLa cells or reconstituted in a reticulocyte lysate. MAT1 constitutes the first example of an assembly factor that appears to be essential for the formation of an active CDK-cyclin complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cell Cycle
  • Cyclin H
  • Cyclin-Dependent Kinases*
  • Cyclins / metabolism*
  • DNA, Complementary
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / metabolism*
  • Structure-Activity Relationship


  • CCNH protein, human
  • Cyclin H
  • Cyclins
  • DNA, Complementary
  • Protein Kinases
  • carboxy-terminal domain kinase
  • Protein-Serine-Threonine Kinases
  • Cyclin-Dependent Kinases
  • cyclin-dependent kinase-activating kinase

Associated data

  • GENBANK/T71380
  • GENBANK/X87843
  • GENBANK/Z44069