Recombination initiated by double-strand breaks

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Mitotic recombination is a key process in genome stability and evolution.
• Understanding the mechanisms of DNA repair and recombination is crucial for genetic research.
• Site-specific double-strand breaks (DSBs) are valuable tools for studying recombination pathways.

Purpose of the Study:

• To investigate the role of HO endonuclease-induced DSBs in monitoring mitotic recombination.
• To analyze the repair mechanisms following DSBs in a specific chromosomal interval.
• To differentiate between recipient and donor roles of the cut chromosome in recombination.

Main Methods:

• Utilized HO endonuclease for site-specific DSB induction in Saccharomyces cerevisiae.
• Constructed a diploid yeast strain with heteroalleles of trp1 and his3 genes.
• Inserted a synthetic HO recognition site between the trp1 and his3 loci on chromosome III.
• Analyzed mitotic recombination events using genetic markers.

Main Results:

• HO-induced cleavage efficiently stimulated recombination in the targeted interval.
• Double-strand gap repair, with the cut chromosome as recipient, explained most recombination events.
• Analysis revealed heteroduplex formation flanking the break site in some recombinants.
• Evidence suggested the cut chromosome could also act as a genetic donor.

Conclusions:

• HO endonuclease is effective for inducing and studying mitotic recombination.
• Both double-strand gap repair and mechanisms involving heteroduplex formation contribute to recombination.
• The role of the cut chromosome as a donor or recipient depends on the specific repair pathway utilized.