What is the role of cyclins and CDKs in the cell cycle?

Cyclins and CDKs regulate the progression of the cell cycle.

Cyclins are proteins that regulate the activity of CDKs (cyclin-dependent kinases), which are enzymes that control the progression of the cell cycle. Cyclins and CDKs work together to ensure that the cell cycle proceeds in a controlled and coordinated manner.

During the G1 phase of the cell cycle, cyclin D is produced, which binds to CDK4 and CDK6 to form a complex that promotes the transition to the S phase. In the S phase, cyclin E is produced, which binds to CDK2 to initiate DNA replication. In the G2 phase, cyclin A is produced, which binds to CDK1 to prepare the cell for mitosis. Finally, in the M phase, cyclin B is produced, which binds to CDK1 to initiate mitosis.

The levels of cyclins and CDKs are tightly regulated by various mechanisms, including transcriptional regulation, post-transcriptional modification, and degradation. For example, the degradation of cyclin B by the anaphase-promoting complex (APC) is necessary for the exit from mitosis.

Mutations in cyclins or CDKs can lead to uncontrolled cell division and the development of cancer. Therefore, understanding the regulation of the cell cycle by cyclins and CDKs is important for the development of cancer therapies.