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T‐loop phosphorylation stabilizes the CDK7–cyclin H–MAT1 complex in vivo and regulates its CTD kinase activity
Author(s) -
Larochelle Stéphane,
Chen Jian,
Knights Ronald,
Pandur Judit,
Morcillo Patrick,
ErdjumentBromage Hediye,
Tempst Paul,
Suter Beat,
Fisher Robert P.
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.14.3749
Subject(s) - cyclin dependent kinase 7 , transcription factor ii h , biology , cyclin dependent kinase , phosphorylation , rna polymerase ii , cyclin dependent kinase complex , microbiology and biotechnology , cyclin dependent kinase 2 , kinase , cyclin a , phosphorylation cascade , biochemistry , protein kinase a , protein phosphorylation , dna repair , cell cycle , dna , promoter , gene expression , gene , nucleotide excision repair , cell
Cyclin‐dependent kinase (CDK)7–cyclin H, the CDK‐activating kinase (CAK) and TFIIH‐associated kinase in metazoans can be activated in vitro through T‐loop phosphorylation or binding to the RING finger protein MAT1. Although the two mechanisms can operate independently, we show that in a physiological setting, MAT1 binding and T‐loop phosphorylation cooperate to stabilize the CAK complex of Drosophila . CDK7 forms a stable complex with cyclin H and MAT1 in vivo only when phosphorylated on either one of two residues (Ser164 or Thr170) in its T‐loop. Mutation of both phosphorylation sites causes temperature‐dependent dissociation of CDK7 complexes and lethality. Furthermore, phosphorylation of Thr170 greatly stimulates the activity of the CDK7–cyclin H–MAT1 complex towards the C‐terminal domain of RNA polymerase II without significantly affecting activity towards CDK2. Remarkably, the substrate‐specific increase in activity caused by T‐loop phosphorylation is due entirely to accelerated enzyme turnover. Thus phosphorylation on Thr170 could provide a mechanism to augment CTD phosphorylation by TFIIH‐associated CDK7, and thereby regulate transcription.