DNA damage checkpoint maintains CDH1 in an active state to inhibit anaphase progression

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The DNA damage checkpoint is crucial for preventing the segregation of damaged chromosomes, typically by inducing cell-cycle arrest.
• Key effectors in budding yeast include Mec1, Chk1, and Rad53, homologous to human ATM/ATR, Chk1, and Chk2 kinases.
• It is understood that the checkpoint inhibits chromosome segregation by blocking separase-mediated cohesin cleavage.

Purpose of the Study:

• To elucidate a regulatory network that prevents chromosome segregation upon DNA damage.
• To investigate a mechanism acting in parallel to cohesin cleavage inhibition.
• To identify the components involved in restricting spindle elongation during DNA damage response.

Main Methods:

• Investigated the roles of Rad53, polo kinase, Cdh1, and bimC kinesin family proteins (Cin8, Kip1) in budding yeast.
• Analyzed the regulatory interactions, including Rad53-dependent phosphorylation of polo kinase.
• Assessed the impact on Cdh1 activity and its regulation of kinesin accumulation and spindle elongation.

Main Results:

• Identified a regulatory circuit involving Rad53, polo kinase, Cdh1, Cin8, and Kip1 that restricts spindle elongation.
• Demonstrated that Rad53-dependent phosphorylation inhibits polo kinase, preventing Cdh1 inactivation.
• Showed that sustained partial Cdh1 activity limits Cin8 and Kip1 accumulation, thereby restraining spindle elongation.

Conclusions:

• The DNA damage checkpoint employs a dual strategy to preserve chromosome stability: inhibiting cohesin cleavage and restricting spindle elongation.
• This parallel regulatory network ensures proper chromosome segregation by controlling spindle dynamics.
• The findings highlight a novel mechanism by which the DNA damage checkpoint maintains genomic integrity.