CDKd2

CDKD2 is a protein that belongs to the cyclin-dependent kinase-activating kinase (CAK) family, functioning to activate cyclin-dependent kinases (CDKs) in eukaryotic cells. CAKs phosphorylate the activation loop (the T-loop) of CDKs, enabling their catalytic activity in response to cyclin binding and thereby promoting cell cycle progression and, in some organisms, transcriptional regulation. CDKD2 is one of several CDKD paralogs found in various species, including organisms where CDKD1, CDKD2, and CDKD3 exist as distinct genes with overlapping or specialized roles.

In many eukaryotes, CDK-activating kinases are integrated into larger complexes that coordinate transcription and DNA repair with cell cycle control. Plant and fungal CDKDs are often homologous to the catalytic subunit that participates in transcriptional regulation as part of the transcription factor IIH (TFIIH) complex. In these contexts, CDKD proteins contribute to phosphorylation of the RNA polymerase II C-terminal domain (CTD) and to the activation of CDKs that drive cell division, linking transcriptional initiation with cell cycle progression. CDKD2’s precise function can vary by organism, developmental stage, and tissue type, reflecting potential redundancy with other CDKD paralogs.

Proteins in the CDKD family typically feature a conserved kinase domain and nuclear localization signals, consistent with roles in nuclear processes such as transcriptional regulation and cell cycle control. They interact with CDKs, cyclins, and TFIIH components, and their activity is regulated by cellular cues that govern growth and development. Disruption of CAK activity can lead to impaired CDK activation and defects in cell division or development, though phenotypes are often modulated by redundancy among paralogs.

See also: CDK-activating kinase, CDKs, TFIIH, CDKD1, CDKD3.