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 (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.
Swiss Institute for Experimental Cancer Research (ISREC), Epalinges, Switzerland.
J P
JP
Tassan
M
M
Jaquenoud
A M
AM
Fry
S
S
Frutiger
G J
GJ
Hughes
E A
EA
Nigg
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D056748:Cyclin H; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000378:metabolism*; D018076:DNA, Complementary; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D000095043:Cyclin-Dependent Kinase-Activating Kinase
C534751:CCNH protein, human; D056748:Cyclin H; D016213:Cyclins; D018076:DNA, Complementary; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D000095043:Cyclin-Dependent Kinase-Activating Kinase; C000722416:CDK7 protein, human