Structure and repair of replication-coupled DNA breaks

Area of Science:

• Molecular Biology
• Genetics
• DNA Repair

Background:

• Single-strand breaks are common endogenous DNA damage.
• Replication fork integrity is crucial for genome stability.

Purpose of the Study:

• To investigate the interaction between DNA replication machinery and single-strand breaks.
• To elucidate mechanisms of double-strand break formation and repair originating from replication stress.

Main Methods:

• CRISPR-Cas9 nicking enzymes to induce targeted single-strand breaks.
• Analysis of replication fork dynamics and DNA repair pathway engagement.

Main Results:

• Replication fork collapse at leading-strand nicks forms resected single-ended double-strand breaks (seDSBs) repaired by homologous recombination (HR).
• Unrepaired seDSBs can lead to double-ended double-strand breaks (deDSBs) and genomic scarring, particularly in HR-deficient cancers.
• BRCA1-independent end resection at nick-induced seDSBs and deDSBs was observed.
• BRCA1 antagonizes 53BP1-mediated suppression of RAD51 filament formation.

Conclusions:

• Distinct mechanisms involving replication fork dynamics contribute to DNA double-strand break formation and repair.
• Understanding these pathways is critical for maintaining genome stability and in cancer therapy.