Compensatory functions and interdependency of the DNA-binding domain of BRCA2 with the BRCA1-PALB2-BRCA2 complex

Cancer Res. 2014 Feb 1;74(3):797-807. doi: 10.1158/0008-5472.CAN-13-1443. Epub 2013 Nov 27.

Abstract

BRCA1, BRCA2, and PALB2 are key players in cellular tolerance to chemotherapeutic agents, including camptothecin, cisplatin, and PARP inhibitor. The N-terminal segment of BRCA2 interacts with PALB2, thus contributing to the formation of the BRCA1-PALB2-BRCA2 complex. To understand the role played by BRCA2 in this complex, we deleted its N-terminal segment and generated BRCA2(Δ)(N) mutant cells. Although previous studies have suggested that BRCA1-PALB2 plays a role in the recruitment of BRCA2 to DNA-damage sites, BRCA2(Δ)(N) mutant cells displayed a considerably milder phenotype than did BRCA2(-/-) null-deficient cells. We hypothesized that the DNA-binding domain (DBD) of BRCA2 might compensate for a defect in BRCA2(ΔN) that prevented stable interaction with PALB2. To test this hypothesis, we disrupted the DBD of BRCA2 in wild-type and BRCA2(Δ)(N) cells. Remarkably, although the resulting BRCA2(Δ)(DBD) cells displayed a moderate phenotype, the BRCA2(Δ)(N+ΔDBD) cells displayed a very severe phenotype, as did the BRCA2(-/-) cells, suggesting that the N-terminal segment and the DBD play a substantially overlapping role in the functionality of BRCA2. We also showed that the formation of both the BRCA1-PALB2-BRCA2 complex and the DBD is required for efficient recruitment of BRCA2 to DNA-damage sites. Our study revealed the essential role played by both the BRCA1-PALB2-BRCA2 complex and the DBD in the functionality of BRCA2, as each can compensate for the other in the recruitment of BRCA2 to DNA-damage sites. This knowledge adds to our ability to accurately predict the efficacy of antimalignant therapies for patients carrying mutations in the BRCA2 gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • BRCA1 Protein / metabolism*
  • BRCA2 Protein / chemistry
  • BRCA2 Protein / genetics
  • BRCA2 Protein / metabolism*
  • Cell Line, Tumor
  • Chromosome Aberrations
  • DNA / metabolism*
  • DNA Damage / drug effects
  • Fanconi Anemia Complementation Group N Protein
  • Gene Deletion
  • Gene Knockout Techniques
  • Genotype
  • Humans
  • Mitosis
  • Multiprotein Complexes / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phenotype
  • Protein Binding
  • Protein Interaction Domains and Motifs*
  • Rad51 Recombinase / genetics
  • Rad51 Recombinase / metabolism
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*

Substances

  • BRCA1 Protein
  • BRCA2 Protein
  • Fanconi Anemia Complementation Group N Protein
  • Multiprotein Complexes
  • Nuclear Proteins
  • PALB2 protein, human
  • Tumor Suppressor Proteins
  • DNA
  • Rad51 Recombinase