A cyclin-dependent kinase activating kinase complex capable of activating cyclin-dependent kinases by threonine phosphorylation, thus regulating cell cycle progression. consists of a kinase, cyclin and optional assembly factors, in human CDK7, CCNH and MNAT1. CAK activity is itself regulated throughout the cell cycle by T-loop phosphorylation of its kinase component (CDK7 in human). Phosphorylation of serine residues during mitosis inactivates the enzyme. Also capable of CAK phosphorylating the carboxyl-terminal domain (CTD) of RNA polymerase II and other transcription activating proteins, as part of the general transcription factor TFIIH.
CAK complex