Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA.
Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
Nucleic Acids Res. 2019 Feb 20;47(3):1294-1310. doi: 10.1093/nar/gky519.
Pds5 is required for sister chromatid cohesion, and somewhat paradoxically, to remove cohesin from chromosomes. We found that Pds5 plays a critical role during DNA replication that is distinct from its previously known functions. Loss of Pds5 hinders replication fork progression in unperturbed human and mouse cells. Inhibition of MRE11 nuclease activity restores fork progression, suggesting that Pds5 protects forks from MRE11-activity. Loss of Pds5 also leads to double-strand breaks, which are again reduced by MRE11 inhibition. The replication function of Pds5 is independent of its previously reported interaction with BRCA2. Unlike Pds5, BRCA2 protects forks from nucleolytic degradation only in the presence of genotoxic stress. Moreover, our iPOND analysis shows that the loading of Pds5 and other cohesion factors on replication forks is not affected by the BRCA2 status. Pds5 role in DNA replication is shared by the other cohesin-removal factor Wapl, but not by the cohesin complex component Rad21. Interestingly, depletion of Rad21 in a Pds5-deficient background rescues the phenotype observed upon Pds5 depletion alone. These findings support a model where loss of either component of the cohesin releasin complex perturbs cohesin dynamics on replication forks, hindering fork progression and promoting MRE11-dependent fork slowing.
Pds5 对于姐妹染色单体的黏合是必需的，有些矛盾的是，它还能从染色体上移除黏连蛋白(cohesin)。我们发现 Pds5 在 DNA 复制过程中发挥着关键作用，这与它先前已知的功能不同。在未受干扰的人类和小鼠细胞中，缺失 Pds5 会阻碍复制叉的前进。抑制 MRE11 核酸酶的活性可以恢复叉的前进，这表明 Pds5 保护叉免受 MRE11 活性的影响。Pds5 的缺失也会导致双链断裂，而 MRE11 的抑制作用再次减少了双链断裂的发生。Pds5 的复制功能与其先前报道的与 BRCA2 的相互作用无关。与 Pds5 不同的是，BRCA2 仅在存在遗传毒性应激时才能保护叉免受核酸酶的降解。此外，我们的 iPOND 分析表明，Pds5 和其他黏连蛋白去除因子 Wapl 加载到复制叉上的情况不受 BRCA2 状态的影响。Pds5 在 DNA 复制中的作用与另一个黏连蛋白释放因子 Wapl 共享，但与黏连蛋白复合物成分 Rad21 不同。有趣的是，在 Pds5 缺失背景下耗尽 Rad21 可以挽救单独耗尽 Pds5 时观察到的表型。这些发现支持这样一种模型，即黏连蛋白释放复合物的任何一个组成部分的缺失都会扰乱复制叉上的黏连蛋白动力学，阻碍叉的前进，并促进依赖 MRE11 的叉减速。
