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

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 (menage a 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.
Mesh Terms:
Amino Acid Sequence, Animals, Base Sequence, Cell Cycle, Cyclin H, Cyclin-Dependent Kinases, Cyclins, DNA, Complementary, HeLa Cells, Humans, Molecular Sequence Data, Protein Kinases, Protein-Serine-Threonine Kinases, Structure-Activity Relationship
EMBO J.
Date: Nov. 15, 1995
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