A prototypical Fanconi anemia pathway in lower eukaryotes?

Area of Science:

• Molecular Biology
• DNA Repair
• Cell Cycle Regulation

Background:

• DNA interstrand cross-links (ICLs) impede DNA replication and transcription, posing a significant threat to genomic stability.
• Eukaryotic ICL repair is intricate, involving multiple pathways that operate in a cell cycle-dependent manner.
• The Fanconi anemia (FA) pathway in mammals is crucial for ICL repair, but its mechanistic details remain elusive.

Purpose of the Study:

• To investigate the role of yeast homologs of FA genes in DNA interstrand cross-link repair.
• To elucidate the interplay between FA homologs and the Pso2-dependent pathway in ICL processing.
• To understand how these pathways prevent replication fork collapse at ICL sites.

Main Methods:

• Genetic analysis of Saccharomyces cerevisiae mutants lacking homologs of FA genes (Mph1, Chl1, Slx4).
• Assessment of sensitivity to DNA cross-linking agents.
• Investigating the functional redundancy and overlap between FA homologs and Pso2 in ICL repair.

Main Results:

• Yeast FA homologs, despite lacking significant ICL sensitivity in single mutants, function in an S-phase-specific ICL repair pathway.
• This pathway shows overlapping or redundant roles with the Pso2-controlled ICL repair pathway.
• The identified pathway prevents the collapse of ICL-stalled replication forks into double-strand breaks.

Conclusions:

• Yeast possesses an evolutionarily conserved ICL repair pathway involving FA homologs, distinct from but cooperating with the Pso2 pathway.
• This pathway is essential for maintaining genome integrity by preventing replication fork collapse during S-phase.
• The findings provide insights into ICL repair mechanisms and potential parallels with mammalian FA pathway function.