Rad52 promotes second-end DNA capture in double-stranded break repair to form complement-stabilized joint molecules

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Biochemistry

Background:

• DNA double-stranded breaks (DSBs) are severe DNA lesions requiring efficient repair.
• Recombinational repair pathways, involving proteins like Rad52 and Rad51, are critical for maintaining genomic integrity.
• Rad52 plays multifaceted roles in DSB repair, including mediating Rad51 assembly and catalyzing DNA strand annealing.

Purpose of the Study:

• To elucidate the specific role of Saccharomyces cerevisiae Rad52 in the second-end capture step of DSB repair.
• To investigate the mechanism by which Rad52 promotes the formation of complement-stabilized joint molecules.
• To determine the species-specificity of Rad52-mediated annealing and second-end capture.

Main Methods:

• In vitro biochemical assays using purified proteins and DNA substrates.
• Analysis of Rad52's ability to anneal RPA-ssDNA complexes to joint molecules.
• Comparative studies using RecO (prokaryotic Rad52 homolog) and different ssDNA-binding proteins (human RPA, SSB).

Main Results:

• Rad52 promotes the annealing of RPA-ssDNA complexes to the displaced strand of joint molecules, forming complement-stabilized joint molecules.
• The prokaryotic homolog RecO cannot form these structures with RPA-ssDNA complexes.
• Rad52's second-end capture activity is species-specific, failing with human RPA or SSB-bound ssDNA.

Conclusions:

• Rad52 facilitates second-end capture by annealing resected DNA breaks (complexed with RPA) to the joint molecule intermediate.
• Rad52-promoted annealing is a key mechanism in forming Holliday junctions during DSB repair.
• The observed species-specificity highlights the intricate adaptations of DNA repair machinery across different organisms.