Distinct repair outcomes from single and convergent replication fork collapse

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Replication fork collapse at DNA breaks poses a threat to genome stability.
• Mechanisms for repairing and resolving collapsed replication forks remain poorly understood.

Purpose of the Study:

• To investigate the distinct repair pathways of single versus converging replication fork collapse.
• To elucidate the resolution mechanisms of single-ended and double-ended double-strand breaks (DSBs) arising from fork collapse.

Main Methods:

• Replication of site-specific nicks using single or converging replication forks in Xenopus laevis egg extracts.
• Analysis of DNA repair outcomes, including homologous recombination, nucleolytic degradation, and annealing-dependent DSB repair.

Main Results:

• Single fork collapse results in single-ended DSBs repaired by homologous recombination or nucleolytic degradation, without DNA synthesis restart.
• Converging fork collapse generates double-ended DSBs repaired by annealing-dependent mechanisms, leading to precise deletions and templated insertions.
• Distinct repair pathways were observed for single and converging collapsed forks.

Conclusions:

• The study reveals context-dependent repair outcomes for collapsed replication forks.
• Understanding these pathways is crucial for maintaining genome stability and preventing mutations.