Replication gap suppression depends on the double-strand DNA binding activity of BRCA2

Area of Science:

• Genomics
• Cancer Biology
• DNA Repair

Background:

• Replication stress (RS) is a key driver of genomic instability and cancer.
• BRCA2 deficiency causes RS and impacts DNA repair via homologous recombination (HR).
• BRCA2's role in limiting single-stranded DNA (ssDNA) gaps at stalled forks is unclear.

Purpose of the Study:

• To investigate the function of BRCA2 in preventing and repairing ssDNA gaps.
• To differentiate the mechanisms of ssDNA gap formation induced by nucleotide depletion versus PARP inhibitors (PARPi).

Main Methods:

• Utilized breast cancer variants with mutations in different BRCA2 domains.
• Assessed the impact of these variants on ssDNA gap formation and repair under different stress conditions.

Main Results:

• The N-terminal DNA binding domain (NTD) of BRCA2, specifically its double-stranded DNA (dsDNA) binding ability, is crucial for preventing and repairing ssDNA gaps during nucleotide depletion.
• This NTD function is not required for limiting PARPi-induced ssDNA gaps.
• Nucleotide depletion and PARPi induce ssDNA gaps through distinct pathways.

Conclusions:

• The NTD of BRCA2 plays a critical role in preventing ssDNA gap formation under nucleotide depletion stress.
• BRCA2's function in managing ssDNA gaps differs depending on the underlying cause of replication stress.