The BRC Repeats of BRCA2 Modulate the DNA-binding Selectivity of RAD51

Cell. 2009 Mar 20;136(6):1032-43. doi: 10.1016/j.cell.2009.02.019.


The breast cancer susceptibility protein, BRCA2, is essential for recombinational DNA repair. BRCA2 delivers RAD51 to double-stranded DNA (dsDNA) breaks through interaction with eight conserved, approximately 35 amino acid motifs, the BRC repeats. Here we show that the solitary BRC4 promotes assembly of RAD51 onto single-stranded DNA (ssDNA), but not dsDNA, to stimulate DNA strand exchange. BRC4 acts by blocking ATP hydrolysis and thereby maintaining the active ATP-bound form of the RAD51-ssDNA filament. Single-molecule visualization shows that BRC4 does not disassemble RAD51-dsDNA filaments but rather blocks nucleation of RAD51 onto dsDNA. Furthermore, this behavior is manifested by a domain of BRCA2 comprising all eight BRC repeats. These results establish that the BRC repeats modulate RAD51-DNA interaction in two opposing but functionally reinforcing ways: targeting active RAD51 to ssDNA and prohibiting RAD51 nucleation onto dsDNA. Thus, BRCA2 recruits RAD51 to DNA breaks and, we propose, the BRC repeats regulate DNA-binding selectivity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Amino Acid Motifs
  • BRCA2 Protein / chemistry
  • BRCA2 Protein / metabolism*
  • DNA, Single-Stranded / metabolism*
  • Humans
  • Models, Biological
  • Rad51 Recombinase / metabolism*
  • Recombination, Genetic


  • BRCA2 Protein
  • DNA, Single-Stranded
  • Adenosine Triphosphate
  • Rad51 Recombinase