Cyclin-dependent kinase 12–cyclin K complex (CDK12–cyclin K)

The cyclin-dependent kinase 12–cyclin K complex is a heterodimeric protein complex consisting of the serine/threonine kinase CDK12 and its regulatory partner cyclin K. This complex principally controls transcription elongation by phosphorylating the C-terminal domain of RNA polymerase II at serine 2, a modification essential for expression of long genes involved in DNA repair and RNA processing[1][2][4][6]. The CDK12–cyclin K complex is a central regulator of genomic stability, with key involvement in DNA damage response pathways. Loss or inhibition of CDK12–cyclin K function impairs expression of critical genes such as BRCA1 and ATR, leading to increased cellular sensitivity to DNA-damaging agents and PARP inhibitors. Mutations or dysfunction of this complex are implicated in several cancers, and multiple small-molecule inhibitors targeting it are under investigation as cancer therapeutics[6][7][5]. The complex’s structure features unique kinase domain extensions that regulate its activity and interactions with cyclin K, and its action is tightly controlled at the molecular level by phosphorylation and association with cyclin K.

Other names

CDK12/CycK complexCDK12–CCNK complexCdk12–cyclin KCdk12/CycK

Inhibits phosphorylation of RNA polymerase II CTD at Ser2, disrupting transcriptional elongation and DNA damage response gene expression[6][7]. Promotes degradation of cyclin K and/or CDK12, leading to decreased expression of DNA repair genes and synthetic lethality in tumors[6][7].