Li Xuan, Stith Carrie M, Burgers Peter M, Heyer Wolf-Dietrich
Department of Microbiology, University of California, Davis, 95616-8665, USA.
Mol Cell. 2009 Nov 25;36(4):704-13. doi: 10.1016/j.molcel.2009.09.036.
Genetic recombination ensures proper chromosome segregation during meiosis and is essential for genome stability and tumor suppression. DNA synthesis after Rad51-mediated DNA strand invasion is a crucial step during recombination. PCNA is known as the processivity clamp for DNA polymerases. Here, we report the surprising observation that PCNA is specifically required to initiate recombination-associated DNA synthesis in the extension of the 3' end of the invading strand in a D loop. We show using a reconstituted system of yeast Rad51, Rad54, RPA, PCNA, RFC, and DNA polymerase delta that loading of PCNA by RFC targets DNA polymerase delta to the D loop formed by Rad51 protein, allowing efficient utilization of the invading 3' end and processive DNA synthesis. We conclude that PCNA has a specific role in the initiation of recombination-associated DNA synthesis and that DNA polymerase delta promotes recombination-associated DNA synthesis.
基因重组确保减数分裂过程中染色体的正确分离,对于基因组稳定性和肿瘤抑制至关重要。Rad51介导的DNA链侵入后的DNA合成是重组过程中的关键步骤。PCNA是已知的DNA聚合酶的持续性夹子。在此,我们报告了一个惊人的发现,即在D环中侵入链3'端的延伸过程中,特异性地需要PCNA来启动与重组相关的DNA合成。我们使用酵母Rad51、Rad54、RPA、PCNA、RFC和DNA聚合酶δ的重组系统表明,RFC加载PCNA可将DNA聚合酶δ靶向由Rad51蛋白形成的D环,从而有效利用侵入的3'端并进行持续性DNA合成。我们得出结论,PCNA在启动与重组相关的DNA合成中具有特定作用,并且DNA聚合酶δ促进与重组相关的DNA合成。