Cohesin Ubiquitylation and Mobilization Facilitate Stalled Replication Fork Dynamics

Area of Science:

• * Molecular Biology
• * Cell Biology
• * Genetics

Background:

• * Replication fork integrity is crucial for genome stability, especially under stress.
• * The Mec1/ATR checkpoint pathway protects replication forks.
• * The role of the structural maintenance of chromosomes (SMC) cohesin complex in fork protection is not fully understood.

Purpose of the Study:

• * To investigate the role of the Rsp5-Bul2 ubiquitin ligase in replication stress response.
• * To elucidate the mechanism by which Rsp5-Bul2 preserves stalled fork integrity.
• * To understand the interplay between Rsp5-Bul2, cohesin, and the Mec1/ATR checkpoint.

Main Methods:

• * Investigated protein-protein interactions between Rsp5-Bul2, cohesin, and Mec1.
• * Analyzed cohesin ubiquitylation and its impact on replication fork stability.
• * Examined the requirement of Wpl1 and Eco1 in the Rsp5-Bul2-mediated fork protection pathway.

Main Results:

• * Rsp5-Bul2 ubiquitin ligase promotes survival to replication stress by preserving stalled fork integrity.
• * Rsp5-Bul2 physically interacts with cohesin and Mec1 kinase, promoting checkpoint-dependent cohesin ubiquitylation.
• * Ubiquitylation by Rsp5-Bul2 facilitates cohesin mobilization and timely association with nascent chromatids, requiring Wpl1 and Eco1.

Conclusions:

• * Rsp5-Bul2 is a key regulator of replication fork protection during stress.
• * Ubiquitylation of cohesin by Rsp5-Bul2 is essential for maintaining stalled fork architecture and genome stability.
• * This mechanism highlights the dynamic role of cohesin in interfacing with replication forks.