Regulates CDK7, the catalytic subunit of the CDK- activating kinase (CAK) enzymatic complex. CAK activates the cyclin-associated kinases CDK1, CDK2, CDK4 and CDK6 by threonine phosphorylation. CAK complexed to the core-TFIIH basal transcription factor activates RNA polymerase II by serine phosphorylation of the repetitive C-terminus domain (CTD) of its large subunit (POLR2A), allowing its escape from the promoter and elongation of the transcripts. Involved in cell cycle control and in RNA transcription by RNA polymerase II. Its expression and activity are constant throughout the cell cycle. Associates primarily with CDK7 and MAT1 to form the CAK complex. CAK can further associate with the core-TFIIH to form the TFIIH basal transcription factor. Belongs to the cyclin family. Cyclin C subfamily. Note: This description may include information from UniProtKB.
Molecular Function: cyclin-dependent protein kinase regulator activity; DNA-dependent ATPase activity; protein binding; RNA polymerase subunit kinase activity
Biological Process: G1/S transition of mitotic cell cycle; G2/M transition of mitotic cell cycle; mRNA capping; nucleotide-excision repair, preincision complex assembly; positive regulation of cyclin-dependent protein kinase activity; positive regulation of transcription from RNA polymerase II promoter; RNA elongation from RNA polymerase I promoter; RNA elongation from RNA polymerase II promoter; termination of RNA polymerase I transcription; transcription from RNA polymerase II promoter; transcription initiation from RNA polymerase I promoter; transcription initiation from RNA polymerase II promoter; transcription-coupled nucleotide-excision repair