DSS1 restrains BRCA2's engagement with dsDNA for homologous recombination, replication fork protection, and R-loop homeostasis

Nat Commun. 2024 Aug 17;15(1):7081. doi: 10.1038/s41467-024-51557-6.

Abstract

DSS1, essential for BRCA2-RAD51 dependent homologous recombination (HR), associates with the helical domain (HD) and OB fold 1 (OB1) of the BRCA2 DSS1/DNA-binding domain (DBD) which is frequently targeted by cancer-associated pathogenic variants. Herein, we reveal robust ss/dsDNA binding abilities in HD-OB1 subdomains and find that DSS1 shuts down HD-OB1's DNA binding to enable ssDNA targeting of the BRCA2-RAD51 complex. We show that C-terminal helix mutations of DSS1, including the cancer-associated R57Q mutation, disrupt this DSS1 regulation and permit dsDNA binding of HD-OB1/BRCA2-DBD. Importantly, these DSS1 mutations impair BRCA2/RAD51 ssDNA loading and focus formation and cause decreased HR efficiency, destabilization of stalled forks and R-loop accumulation, and hypersensitize cells to DNA-damaging agents. We propose that DSS1 restrains the intrinsic dsDNA binding of BRCA2-DBD to ensure BRCA2/RAD51 targeting to ssDNA, thereby promoting optimal execution of HR, and potentially replication fork protection and R-loop suppression.

MeSH terms

  • BRCA2 Protein* / chemistry
  • BRCA2 Protein* / genetics
  • BRCA2 Protein* / metabolism
  • Cell Line, Tumor
  • DNA Damage
  • DNA Replication*
  • DNA* / metabolism
  • DNA, Single-Stranded* / genetics
  • DNA, Single-Stranded* / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Homeostasis
  • Homologous Recombination*
  • Humans
  • Mutation*
  • Proteasome Endopeptidase Complex
  • Protein Binding
  • Protein Domains
  • Rad51 Recombinase* / genetics
  • Rad51 Recombinase* / metabolism

Substances

  • BRCA2 Protein
  • BRCA2 protein, human
  • DNA
  • Rad51 Recombinase
  • DNA, Single-Stranded
  • SEM1 protein, human
  • DNA-Binding Proteins
  • RAD51 protein, human
  • Proteasome Endopeptidase Complex