The RAD52 double-ring remodels replication forks restricting fork reversal

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Genome Stability

Background:

• RAD52 is a key human DNA repair protein.
• It protects stalled replication forks from degradation during replication stress.
• The mechanism of RAD52's fork protection is not fully understood.

Purpose of the Study:

• To elucidate the structural and molecular mechanism of RAD52-mediated replication fork protection.
• To investigate how RAD52 remodels stalled replication forks.

Main Methods:

• Biochemical analyses
• Single-molecule analyses
• P1 nuclease sensitivity assays
• Mass photometry
• Single-particle cryo-electron microscopy

Main Results:

• RAD52 dynamically remodels replication forks through strand exchange activity.
• RPA modulates strand exchange kinetics without altering the outcome.
• A unique head-to-head arrangement of two RAD52 rings forms a nucleoprotein structure at the fork.
• This structure possesses an extended positively charged surface accommodating the replication fork.

Conclusions:

• The identified RAD52 structure is critical for its strand exchange activity.
• This structure likely facilitates competition with SMARCAL1, preventing excessive fork degradation.
• Findings provide insights into maintaining genome stability during replication stress.