CDK inhibitor p21 is degraded by a proliferating cell nuclear antigen-coupled Cul4-DDB1Cdt2 pathway during S phase and after UV irradiation.
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Nishitani H, Shiomi Y, Iida H, Michishita M, Takami T, Tsurimoto T
CDK inhibitor p21 is degraded by a proliferating cell nuclear antigen-coupled Cul4-DDB1Cdt2 pathway during S phase and after UV irradiation.
J Biol Chem. 2008 Oct 24;283(43):29045-52. doi: 10.1074/jbc.M806045200. Epub 2008 Aug 14.
- PubMed ID
- 18703516 [ View in PubMed]
- Abstract
Previous reports showed that chromatin-associated PCNA couples DNA replication with Cul4-DDB1(Cdt2)-dependent proteolysis of the licensing factor Cdt1. The CDK inhibitor p21, another PCNA-binding protein, is also degraded both in S phase and after UV irradiation. Here we show that p21 is degraded by the same ubiquitin-proteasome pathway as Cdt1 in HeLa cells. When PCNA or components of Cul4-DDB1(Cdt2) were silenced or when the PCNA binding site on p21 was mutated, degradation of p21 was prevented both in S phase and after UV irradiation. p21 was co-immunoprecipitated with Cul4A and DDB1 proteins when expressed in cells. The purified Cul4A-DDB1(Cdt2) complex ubiquitinated p21 in vitro. Consistently, p21 protein levels are low during S phase and increase around G(2) phase. Mutational analysis suggested that in addition to the PCNA binding domain, its flanking regions are also important for recognition by Cul4-DDB1(Cdt2). Our findings provide a new aspect of proteolytic control of p21 during the cell cycle.