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^Bul2 ubiquitin ligase in promoting survival to replication stress by preserving stalled fork integrity. Rsp5^Bul2 physically interacts with cohesin and the Mec1 kinase, thus promoting checkpoint-dependent cohesin ubiquitylation and cohesin-mediated fork protection. Ubiquitylation mediated by Rsp5^Bul2 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^Bul2 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.

复制叉的完整性在压力条件下受到挑战，并受到Mec1 / ATR检查点的保护，以保持基因组的稳定性。在叉形保护中仍然缺乏了解的是染色体（SMC）粘着蛋白复合物的结构维持作用。我们发现Rsp5 ^Bul2泛素连接酶在通过维持停滞的叉子完整性而促进存活至复制应激中的作用。Rsp5 ^Bul2在物理上与^黏附素和Mec1激酶相互作用，从而促进检查点依赖性黏附素泛素化和黏附素介导的叉保护。Rsp5 ^Bul2介导的泛^素化通过刺激Cdc48 / p97泛素选择性segregase及其与新生染色单体的及时结合，可促进邻近染色质停叉前叉的黏附素动员。这种Rsp5 ^Bul2前叉保护机制需要Wpl1黏附素动员剂以及Eco1乙酰基转移酶的功能来确保姐妹染色单体的捕获。我们的数据表明，泛素化有助于在保持停滞前叉功能体系结构的机制中使粘着蛋白与复制叉动态衔接。