二本鎖ＤＮＡ切断により誘導される複製プログラム変動のメカニズム

不同类型的DNA损伤可诱导休眠复制起始点的激活。先前的研究表明，在休眠复制起始点附近的单条不可修复的双链断裂（DSB）能够促进起始点激活，可能挽救断裂染色体片段的复制（Doksani et al., Cell 2009）。在这项研究中，我们旨在阐明DSB形成后导致休眠起源放电的机制。在这里，我们发现DNA损伤检查点不抵消dsb诱导的休眠起始点激活，但休眠起始点激活活动被组蛋白乙酰化状态抵消。我们还发现端粒相关蛋白，Rif1和Ku复合体，即使在没有DSB的情况下，也是休眠起源的潜在调节因子。我们发现Rif1和yKu70优先结合在休眠起源和DSB位点之间的区域，而不是在DSB位点的另一侧。这些区域的Rif1和yKu70的结合谱不受DSB形成的影响。此外，我们发现yKu70的缺失会阻止Rif1在休眠起源和DSB位点之间的区域结合。我们的研究结果表明，Rif1和yKu70在控制DSB位点附近的休眠起源活性中起重要作用。

Various types of DNA damage can induce activation of dormant replication origins. Previous studies showed that a single and irrepairable double-strand break (DSB) in the proximity of a dormant replication origin is able to promote origin firing, likely to rescue replication of the broken chromosome fragment (Doksani et al., Cell 2009). In this study, We aim at elucidating the mechanisms leading to dormant origin firing following DSB formation.Here we showed that DNA damage checkpoints do not counteract DSB-induced dormant origin firing but the dormant origin firing activities are counteracted by histone acetylation state. We also identified telomere-related proteins, Rif1 and Ku complex, as potential regulators of dormant origins even in the absence of DSB. We found that Rif1 and yKu70 bind preferentially at regions between dormant origins and DSB site but not at the other side of the DSB site. The binding profiles of Rif1 and yKu70 at those regions are not affected by DSB formation. Besides, we found that absence of yKu70 prevents Rif1 from binding at regions between dormant origins and DSB site. Our results indicate an important role of Rif1 and yKu70 in controlling dormant origin activity near to DSB site.