T-loop phosphorylation stabilizes the CDK7–cyclin H–MAT1 complex in vivo and regulates its CTD kinase activity

AUTOR(ES)

Larochelle, Stéphane

FONTE

Oxford University Press

RESUMO

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.

Documentos Relacionados

• The cdk7-cyclin H-MAT1 complex associated with TFIIH is localized in coiled bodies.
• Characterization of Cdk9 T-loop phosphorylation in resting and activated CD4+ T lymphocytes
• The T-loop in details
• p53 is phosphorylated by CDK7-cyclin H in a p36MAT1-dependent manner.
• In vitro assembly of a functional human CDK7-cyclin H complex requires MAT1, a novel 36 kDa RING finger protein.