Slx5/Slx8 Promotes Replication Stress Tolerance by Facilitating Mitotic Progression

Area of Science:

• Cellular biology
• Molecular genetics
• Biochemistry

Background:

• Loss of Minichromosome maintenance protein 10 (Mcm10) induces replication stress, a critical cellular condition.
• The SUMO-targeted ubiquitin ligase complex Slx5/8 and E3 SUMO ligase Mms21 are crucial for the survival of Saccharomyces cerevisiae mcm10-1 mutants.

Purpose of the Study:

• To investigate the role of the Slx5/8 complex in managing replication stress caused by Mcm10 deficiency.
• To identify Slx5/8-regulated proteins and their function in the context of Mcm10 loss.

Main Methods:

• Quantitative mass spectrometry to analyze the SUMO proteome of mcm10-1 mutants.
• Analysis of the chromosome passenger complex (CPC) components Bir1 and Sli15.
• Assessment of spindle assembly checkpoint (SAC) activation and mitotic progression.

Main Results:

• Slx5/8 regulates subunits of the CPC, including Bir1 and Sli15, which are involved in SAC activation.
• Slx5 counteracts SAC activation in mcm10-1 mutants under moderate replication stress.
• Sumoylated Bir1 undergoes proteasomal degradation, facilitated by Slx5.
• Slx5-dependent mitotic relief is observed in response to both Mcm10 deficiency and low-dose methyl methanesulfonate treatment.

Conclusions:

• The Slx5/8 complex plays a key role in allowing cells to pass through mitosis when facing tolerable levels of replication stress.
• A model is proposed where Slx5/8 facilitates mitotic progression by regulating key checkpoint proteins during replication stress.