The modulation of PCNA ubiquitination by p21 and its significance for DNA repair

而体外实验则着重证明了p21对PCNA依赖性DNA的抑制作用 在细胞中进行的实验很难得出类似的结论。 这可能取决于，至少部分地，在S期的收敛信号，防止p21上调。我们 已经发现了一个有趣的观察结果，即一些遗传毒性治疗，诱导短暂或 S期永久阻滞协同促进p21下调和PCNA泛素化。此外，委员会认为， 稳定的p21表达负调节PCNA泛素化，这是一种转录后修饰， 滑动夹相关的DNA修复相关的活动。这种观察促使我们研究小说 p21对PCNA的调控。 我们拟探讨p21依赖性抑制紫外线照射后增殖细胞核抗原亚群的机制。 辐照这也将有助于识别其他调节PCNA泛素化的分子 是p21的目标。p21降解和PCNA泛素化之间的联系也将使p21降解和PCNA泛素化之间的联系成为可能。 识别协调这些事件的上游途径。稳定的p21对细胞存活的影响 在上述遗传毒性处理期间的表达可能揭示p21的生物学相关性 下调，可能对癌症治疗有意义。

While in vitro experiments emphatically demonstrated the inhibitory effect of p21 on PCNA dependent DNA replication and repair it was much harder to arrive to similar conclusions in experiments performed in cells. This might depend, at least in part, on the convergent signals that prevent p21 up-regulation in S phase. We have come across the intriguing observation that a number of genotoxic treatments that induce transient or permanent arrest in S phase coordinately promote p21 down-regulation and PCNA ubiquitination. Moreover, stable p21 expression negatively modulates PCNA ubiquitination, a post-transcriptional modification of the sliding clamp relevant for its DNA repair-related activities. This observation prompt us to the study of novels aspects of PCNA regulation by p21. We propose to explore the mechanisms for p21 dependent inhibition of PCNA ubqiutination after UV irradiation. This will also facilitate the identification of other molecules that modulate PCNA ubiquitination and are targets of p21. The link between p21 degradation and PCNA ubiquitination will also allow the identification of pathways upstream that coordinate these events. The effects on cell survival of a stable p21 expression during the above mentioned genotoxic treatments might reveal the biological relevance of p21 down-regulation and might be significant for cancer therapy.