Ngo Greg H P, Lydall David
Institute for Cell and Molecular Biosciences (ICaMB), Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
Institute for Cell and Molecular Biosciences (ICaMB), Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
Nucleic Acids Res. 2015 May 26;43(10):5017-32. doi: 10.1093/nar/gkv409. Epub 2015 Apr 29.
DNA-end resection, the generation of single-stranded DNA at DNA double strand break (DSB) ends, is critical for controlling the many cellular responses to breaks. Here we show that the conserved DNA damage checkpoint sliding clamp (the 9-1-1 complex) plays two opposing roles coordinating DSB resection in budding yeast. We show that the major effect of 9-1-1 is to inhibit resection by promoting the recruitment of Rad9(53BP1) near DSBs. However, 9-1-1 also stimulates resection by Exo1- and Dna2-Sgs1-dependent nuclease/helicase activities, and this can be observed in the absence of Rad9(53BP1). Our new data resolve the controversy in the literature about the effect of the 9-1-1 complex on DSB resection. Interestingly, the inhibitory role of 9-1-1 on resection is not observed near uncapped telomeres because less Rad9(53BP1) is recruited near uncapped telomeres. Thus, 9-1-1 both stimulates and inhibits resection and the effects of 9-1-1 are modulated by different regions of the genome. Our experiments illustrate the central role of the 9-1-1 checkpoint sliding clamp in the DNA damage response network that coordinates the response to broken DNA ends. Our results have implications in all eukaryotic cells.
DNA 末端切除，即在 DNA 双链断裂（DSB）末端生成单链 DNA，对于控制细胞对双链断裂的多种反应至关重要。我们在此表明，保守的 DNA 损伤检查点滑动夹（9-1-1 复合物）在芽殖酵母中发挥着两种相反的作用来协调 DSB 切除。我们发现 9-1-1 的主要作用是通过促进 Rad9（53BP1）在 DSB 附近的募集来抑制切除。然而，9-1-1 也通过 Exo1 和 Dna2-Sgs1 依赖性核酸酶/解旋酶活性刺激切除，并且在没有 Rad9（53BP1）的情况下也能观察到这种情况。我们的新数据解决了文献中关于 9-1-1 复合物对 DSB 切除影响的争议。有趣的是，在无帽端粒附近未观察到 9-1-1 对切除的抑制作用，因为在无帽端粒附近募集的 Rad9（53BP1）较少。因此，9-1-1 既能刺激也能抑制切除，并且 9-1-1 的作用受基因组不同区域的调节。我们的实验说明了 9-1-1 检查点滑动夹在协调对断裂 DNA 末端反应的 DNA 损伤反应网络中的核心作用。我们的结果对所有真核细胞都有影响。
