Cyclin-dependent kinases 1, 2, and 4 (CDK1, CDK2, CDK4)

**Cyclin-dependent kinases 1, 2, and 4** are central enzymes in the mammalian cell cycle, activated by binding to specific cyclins. - **CDK4**, associated with Cyclin D, phosphorylates retinoblastoma protein (RB) during early G1 phase, relieving RB-mediated repression and promoting progression into late G1[1][4][6]. - **CDK2** interacts with Cyclin E and Cyclin A, regulating G1/S transition and DNA replication during S phase[1][4][6]. - **CDK1**, mainly partnered with Cyclin B and Cyclin A, is essential for G2/M transition and mitosis[4][3][6]. Dysregulation—often by amplification, mutation, or overexpression—of these kinases or their cyclin partners leads to sustained proliferative signaling, a hallmark of many cancers[1][4][6]. Selective inhibition of CDK4/6 (and to a lesser extent, CDK1/2) is a validated therapeutic approach, particularly in hormone receptor-positive breast cancer[1][4].

Other names

CDC2p34^CDC2^

Competitive inhibition of ATP-binding site. Allosteric inhibition or stabilization of inactive conformation. Inhibition prevents phosphorylation of key cell cycle substrates such as retinoblastoma protein (RB), resulting in cell cycle arrest.