Bacillus subtilis RecU Holliday-junction resolvase modulates RecA activities

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Protein-Protein Interactions

Background:

• Bacillus subtilis RecU protein possesses DNA strand annealing and Holliday-junction resolution activities.
• RecA protein is central to homologous recombination and DNA repair.
• Understanding the interplay between RecA and other DNA repair proteins is crucial for elucidating DNA repair pathways.

Purpose of the Study:

• To investigate the interaction between Bacillus subtilis RecA and RecU proteins.
• To determine the effect of RecU on RecA's DNA binding and catalytic activities.
• To elucidate the role of RecU in modulating RecA function during DNA repair.

Main Methods:

• In vitro biochemical assays were used to study protein-protein interactions.
• RecA loading onto single-stranded DNA (ssDNA) was monitored.
• RecA-catalyzed D-loop formation and three-strand exchange reactions were analyzed.
• ssDNA-dependent ATPase activity of RecA was measured.
• The effect of single-stranded binding (SSB) protein was assessed.

Main Results:

• RecU enhanced RecA loading onto ssDNA and stimulated RecA-catalyzed D-loop formation.
• RecU inhibited RecA-mediated three-strand exchange and ssDNA-dependent ATP hydrolysis.
• Single-stranded binding (SSB) protein did not reverse RecU's inhibitory effects on RecA.
• RecU-mediated DNA strand annealing was independent of RecA and SSB.

Conclusions:

• RecU protein acts as a modulator of RecA protein activities.
• RecU promotes RecA-mediated strand invasion while inhibiting branch migration.
• RecU may prevent RecA filament disassembly, suggesting a role in resolvasome assembly control.
• These findings provide insights into the regulation of DNA repair processes.