Soria Gaston, Speroni Juliana, Podhajcer Osvaldo L, Prives Carol, Gottifredi Vanesa
Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir-CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
J Cell Sci. 2008 Oct 1;121(Pt 19):3271-82. doi: 10.1242/jcs.027730. Epub 2008 Sep 9.
Although p21 upregulation is required to block cell-cycle progression following many types of genotoxic insult, UV irradiation triggers p21 proteolysis. The significance of the increased p21 turnover is unclear and might be associated with DNA repair. While the role of p21 in nucleotide excision repair (NER) remains controversial, recent reports have explored its effect on translesion DNA synthesis (TLS), a process that avoids replication blockage during S phase. Herein, we analyze the effect of p21 on different PCNA-driven processes including DNA replication, NER and TLS. Whereas only the CDK-binding domain of p21 is required for cell-cycle arrest in unstressed cells, neither the CDK-binding nor the PCNA-binding domain of p21 is able to block early and late steps of NER. Intriguingly, through its PCNA-binding domain, p21 inhibits the interaction of the TLS polymerase, pol eta (pol eta), with PCNA and impairs the assembly of pol eta foci after UV. Moreover, this obstruction correlates with accumulation of phosphorylated H2AX and increased apoptosis. By showing that p21 is a negative regulator of PCNA-pol eta interaction, our data unveil a link between efficient TLS and UV-induced degradation of p21.
尽管在多种类型的基因毒性损伤后，需要上调p21来阻断细胞周期进程，但紫外线照射会引发p21蛋白水解。p21周转增加的意义尚不清楚，可能与DNA修复有关。虽然p21在核苷酸切除修复（NER）中的作用仍存在争议，但最近的报道探讨了其对跨损伤DNA合成（TLS）的影响，TLS是一个在S期避免复制阻滞的过程。在此，我们分析了p21对不同的PCNA驱动过程的影响，包括DNA复制、NER和TLS。在未受应激的细胞中，仅p21的CDK结合结构域对于细胞周期停滞是必需的，而p21的CDK结合结构域和PCNA结合结构域均不能阻断NER的早期和晚期步骤。有趣的是，通过其PCNA结合结构域，p21抑制跨损伤合成聚合酶pol eta（pol eta）与PCNA的相互作用，并损害紫外线照射后pol eta焦点的组装。此外，这种阻碍与磷酸化H2AX的积累和凋亡增加相关。通过表明p21是PCNA-pol eta相互作用的负调节因子，我们的数据揭示了有效的TLS与紫外线诱导的p21降解之间的联系。
