Cyclin K

Cyclin K is a regulatory protein encoded by the CCNK gene, classified as a member of the transcription cyclin family[2][5][6]. It functions primarily as a regulatory subunit for cyclin-dependent kinases (including CDK9, CDK12, and CDK13), forming complexes that are essential for transcription regulation and cell cycle progression[1][2][3]. Through its interaction with these CDKs, Cyclin K promotes phosphorylation of the C-terminal domain of RNA polymerase II, facilitating transcriptional elongation[1][2]. Cyclin K also participates in the DNA damage response, mitosis, and cell proliferation, and is reported to be indispensable for leukemia growth and other cancer types[2][6]. Structural studies of Cyclin K reveal characteristic cyclin domains and unique helices relevant for its regulatory interactions[1][4]. Cyclin K is considered a promising therapeutic target, especially for cancer, owing to its key role in transcription and cell survival pathways[6]. Direct drugs targeting Cyclin K are still under research; however, modulation of its partner kinases (e.g., CDK9, CDK12) can indirectly impact Cyclin K functions. Caution is warranted when considering Cyclin K as a drug target, as its inhibition could impair essential transcriptional and DNA repair processes in normal cells[6].

Other names

CCNKCyclin-K

Inhibition of Cyclin K–partnered kinases (such as CDK9 and CDK12) blocks phosphorylation of RNA polymerase II, disrupting transcription elongation and cell proliferation; Modulation of Cyclin K affects DNA damage response and cell survival in cancers