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

各种类型的DNA损伤可以诱导休眠复制起点的激活。先前的研究表明，在休眠复制起始点附近的单个且不可修复的双链断裂(DSB)能够促进原点激发，有可能挽救断裂的染色体片段的复制(Doksani等人，Cell 2009)。在这项研究中，我们旨在阐明在DSB形成后导致休眠起源激发的机制。在这里，我们表明DNA损伤检查点不能抵消DSB诱导的休眠起源激发，但休眠起源激发活动被组蛋白乙酰化状态抵消。我们还发现，即使在没有DSB的情况下，端粒相关蛋白Rif1和Ku复合体也是潜在的休眠起源的调节因子。我们发现Rif1和yKu70优先结合在休眠起始和DSB位点之间的区域，而不是在DSB位点的另一侧。Rif1和yKu70在这些区域的结合谱不受DSB形成的影响。此外，我们发现yKu70的缺失阻止了Rif1结合在休眠起始点和DSB位点之间的区域。我们的结果表明，Rif1和yKu70在控制DSB位点附近的休眠起源活动方面发挥了重要作用。

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.