cyklinkinaser

Cyklinkinaser, or cyclin-dependent kinases (CDKs) in English, are a family of serine/threonine protein kinases that regulate cell cycle progression and, in some cases, transcription. They are inactive on their own and require binding to regulatory subunits called cyclins to become catalytically active. The periodic rise and fall of cyclin levels during the cell cycle drives the orderly activation of CDKs and the phosphorylation of specific substrates.

The best-characterized role of cyklinkinaser is in controlling transitions between cell cycle phases, notably the G1/S and G2/M transitions. Once activated by cyclins, CDKs phosphorylate key targets such as the retinoblastoma protein (RB1), leading to the release of E2F transcription factors and entry into S phase, or phosphorylate mitotic regulators to promote entry into mitosis. Beyond cell cycle control, certain CDKs participate in the regulation of transcription and RNA processing.

Regulation of cyklinkinaser activity is multi-layered. Cyclin synthesis, phosphorylation, and proteolysis coordinate their activation. Inhibitors such as p21, p27, and p16 bind CDKs to block activity. Kinases like Wee1 can phosphorylate CDKs to inhibit them, while phosphatases such as Cdc25 reverse this inhibition. Dysregulation of CDK activity is a common feature in cancers.

Clinically, CDKs are targets for therapy. Inhibitors of CDK4 and CDK6 (for example, palbociclib, ribociclib, abemaciclib) are approved for certain cancers, while inhibitors of other CDKs are under investigation. CDKs are conserved across eukaryotes and remain a central focus in cell biology and oncology research.