title: Regulation of CDK7 substrate specificity by MAT1 and TFIIH.
abstract: The cyclin-dependent kinase (CDK)-activating kinase CAK has been proposed to function in the control of cell cycle progression, DNA repair and RNA polymerase II (pol II) transcription. Most CAK exists as complexes of three subunits: CDK7, cyclin H (CycH) and MAT1. This tripartite CAK occurs in a free form and in association with 'core' TFIIH, which functions in both pol II transcription and DNA repair. We investigated the substrate specificities of different forms of CAK. Addition of the MAT1 subunit to recombinant bipartite CDK7-CycH switched its substrate preference to favour the pol II large subunit C-terminal domain (CTD) over CDK2. We suggest that the MAT1 protein, previously shown to function as an assembly factor for CDK7-CycH, also acts to modulate CAK substrate specificity. The substrate specificities of natural TFIIH and free CAK were also compared. TFIIH had a strong preference for the CTD over CDK2 relative to free CAK. TFIIH, but not free CAK, could efficiently hyperphosphorylate the CTD. In the context of TFIIH, the kinase also acquired specificity for the general transcription factors TFIIE and TFIIF which were not recognized by free CAK. We conclude that the substrate preference of the CDK7-CycH kinase is governed by association with both MAT1 and 'core' TFIIH.
authors.affiliation: Amgen Institute and Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: K Y
authors.initials: KY
authors.lastname: Yankulov
authors.forename: D L
authors.initials: DL
authors.lastname: Bentley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D015153:Blotting, Western; D018844:Cyclin-Dependent Kinases; D004265:DNA Helicases / Q000302:isolation & purification / Q000378:metabolism; D004260:DNA Repair; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D018411:Spodoptera; D013379:Substrate Specificity; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D019473:Transcription Factors, TFII; D014162:Transfection; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: D000906:Antibodies; D046911:Macromolecular Substances; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D019473:Transcription Factors, TFII; C066644:transcription factor TFIIE; D051758:Transcription Factor TFIIH; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D004265:DNA Helicases; C056604:transcription factor TFIIF; D000095043:Cyclin-Dependent Kinase-Activating Kinase