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p21 |
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| p21, also known as cyclin-dependent kinase inhibitor 1A or CDKN1A, directly inhibits the activity of cyclin-cdk2 and cyclin-cdk4 complexes. It mainly inhibits the activity of cyclin/cdk2 complexes and negatively modulates cell cycle progression. p21 also plays other fundamental roles including transcriptional regulation and the modulation of apoptosis.
p21 forms part of a family of structurally related proteins comprising p21, p27 and p57 that all share the ability to inhibit a wide range of cyclin -dependent kinase holoenzymes.
Besides its cdk inhibitor function, p21 is recognized to play a wide variety of physiological roles, many of which rely on its nuclear localization. p21 can bind to proliferating cell nuclear antigen (PCNA) thereby blocking DNA synthesis. p21 functions as a regulator of cell cycle progression at S phase. The expression of p21 is controlled by the tumor suppressor protein p53. Each of these functions of p21 is achieved through direct p21/protein interactions and the subcellular localization of p21 plays an important part in dictating the binding partners to which p21 is exposed. |
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1) Child ES and Mann DJ, 2006, Cell Cycle 5(12):1313-9
2) Liu G and Lozano G, 2005, Cancer Cell 7(2):113-114
3) Gartel AL and Tyner AL, 2002, Mol Cancer Ther 1(8):639-649
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