Instituto de Biología Funcional y Genómica (IBFG-CSIC), Universidad de Salamanca, Calle Zacarías González 2, 37007 Salamanca, Spain; Centro de Investigaciones Biológicas (CIB-CSIC), Calle Ramiro de Maeztu 9, 28040 Madrid, Spain.
Centro de Investigaciones Biológicas (CIB-CSIC), Calle Ramiro de Maeztu 9, 28040 Madrid, Spain.
Mol Cell. 2017 Nov 16;68(4):758-772.e4. doi: 10.1016/j.molcel.2017.10.012. Epub 2017 Nov 9.
Replication fork integrity is challenged in conditions of stress and protected by the Mec1/ATR checkpoint to preserve genome stability. Still poorly understood in fork protection is the role played by the structural maintenance of chromosomes (SMC) cohesin complex. We uncovered a role for the Rsp5 ubiquitin ligase in promoting survival to replication stress by preserving stalled fork integrity. Rsp5 physically interacts with cohesin and the Mec1 kinase, thus promoting checkpoint-dependent cohesin ubiquitylation and cohesin-mediated fork protection. Ubiquitylation mediated by Rsp5 promotes cohesin mobilization from chromatin neighboring stalled forks, likely by stimulating the Cdc48/p97 ubiquitin-selective segregase, and its timely association to nascent chromatids. This Rsp5 fork protection mechanism requires the Wpl1 cohesin mobilizer as well as the function of the Eco1 acetyltransferase securing sister chromatid entrapment. Our data indicate that ubiquitylation facilitates cohesin dynamic interfacing with replication forks within a mechanism preserving stalled-fork functional architecture.
在压力条件下，复制叉的完整性受到挑战，Mec1/ATR 检查点保护其基因组稳定性。在叉保护中，结构维持染色体（SMC）黏合复合物的作用仍知之甚少。我们发现 Rsp5 泛素连接酶在通过保持停滞叉的完整性来促进复制应激生存中的作用。Rsp5 与黏合蛋白和 Mec1 激酶相互作用，从而促进检查点依赖的黏合蛋白泛素化和黏合蛋白介导的叉保护。Rsp5 介导的泛素化促进黏合蛋白从邻近停滞叉的染色质上的动员，可能通过刺激 Cdc48/p97 泛素选择性分选酶及其与新生染色单体的及时关联来实现。这种 Rsp5 叉保护机制需要 Wpl1 黏合蛋白动员器以及 Eco1 乙酰转移酶确保姐妹染色单体的捕获功能。我们的数据表明，泛素化有助于黏合蛋白在保护停滞叉功能结构的机制中与复制叉进行动态相互作用。
