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p21 is a potent cyclin-dependent kinase inhibitor (CKI). The p21 (CIP1/WAF1) protein binds to and inhibits the activity of cyclin-CDK2, -CDK1, and -CDK4 /6 complexes, and thus functions as a regulator of cell cycle progression at G 1 and S phase.
An important downstream target of ATM and ATR is p53, as it is required for inducing apoptosis following DNA damage. [56] The cyclin-dependent kinase inhibitor p21 is induced by both p53-dependent and p53-independent mechanisms and can arrest the cell cycle at the G1/S and G2/M checkpoints by deactivating cyclin/cyclin-dependent kinase ...
Chk1/2 phosphorylate cdc25 which, in addition to being inhibited, is also sequestered in the cytoplasm by the 14-3-3 proteins. 14-3-3 are upregulated by p53, which, as previously mentioned, is activated by Chk1 and ATM/ATR. p53 also transactivates p21, and both p21 and the 14-3-3 in turn inhibit cyclin B-cdc2 complexes through the ...
The discovery of the first CKIs in yeast and P21 in mammals has led to research on family of molecules. [8] Further research has demonstrates that Cdks, cyclins and CKIs play essential roles in processes such as transcription , epigenetic regulation , metabolism , stem cell self-renewal, neuronal functions and spermatogenesis .
The maintenance of such arrest in the G2 phase is further sustained by p53 and p21. In the absence of p53 or p21, it was demonstrated that radiated cells progressed into mitosis. [ 17 ] The absence of p21 or 14-3-3 cannot sufficiently inhibit the CyclinB-Cdc2 complex, thus exhibiting the regulatory control of p53 and p21 in the G2 checkpoint in ...
P53, p63, and p73 have similar features in their gene structures and functions but have also diverged evolutionarily. The p53 family evolved from an ancestor gene in unicellular life. [ 4 ] The ancestor gene functioned in germ line DNA protection early invertebrates. [ 5 ]
A cyclin-dependent kinase inhibitor (CKI) is a protein that interacts with a cyclin-CDK complex to inhibit kinase activity, often during G1 phase or in response to external signals or DNA damage. In animal cells, two primary CKI families exist: the INK4 family (p16, p15, p18, p19) and the CIP/KIP family (p21, p27, p57). The INK4 family proteins ...
[9] p53 is also phosphorylated by the effector kinase CHK2. These phosphorylation events lead to stabilization and activation of p53 and subsequent transcription of numerous p53 target genes including CDK inhibitor p21 which lead to long-term cell-cycle arrest or even apoptosis. [15] ATM-mediated two-step response to DNA double strand breaks.