The cyclin-dependent kinase (CDK)-activating kinase (CAK) complex is a three-subunit kinase module present as a subcomplex of TFIIH, as free trimeric CAK or in complex with the ATP-dependent DNA helicase XPD (
Xpd in D.mel). The TFIIH-associated CAK complex phosphorylates the C-terminal domain of RNA pol II. The free form of CAK activates the cell cycle CDKs. The CAK-XPD complex regulates the cell cycle progression in mitosis. (Adapted from
FBrf0227236 and
PMID:21592869).