Cyclin A

One such regulatory component is cyclin A which plays a role in the regulation of two different cell cycle stages.

[7] Cyclin A can regulate multiple cell cycle steps because it associates with, and thereby activates, two distinct CDKs – CDK2 and CDK1.

[10] Cyclin A resides in the nucleus during S phase where it is involved in the initiation and completion of DNA replication.

[7][11][12] This is thought to occur through the phosphorylation of particular DNA replication machinery components, such as CDC6, by the cyclin A/CDK2 complex.

[7] Cyclin A/CDK2 complex was thought to be restricted to the nucleus and thus exclusively involved in S phase progression.

New research has since debunked this assumption, shedding light on cyclin A/CDK2 migration to the centrosomes in late G2.

These mutants entered mitosis late due to a delayed activation of the cyclin B/CDK1 complex.

Coupling of microtubule nucleation in the centrosome with mitotic events in the nucleus was lost in the cyclin A knockout/CDK2 inhibited mutant cells.

Cyclin A has been shown to play a crucial role in the G2/M transition in Drosophila and Xenopus embryos.

[3][6] Transcription of cyclin A is tightly regulated and synchronized with cell cycle progression.

The absence of cyclin A prior to the R point is due to the inhibition of E2F by hypophosphorylated pRb.

P53 is activated by DNA damage and turns on several downstream pathways, including cell cycle arrest.