The BRC repeats of BRCA2 modulate the DNA-binding selectivity of RAD51.
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.
Carreira
Aura
A
Department of Microbiology, University of California, Davis, CA 95616, USA.
Hilario
Jovencio
J
Amitani
Ichiro
I
Baskin
Ronald J
RJ
Shivji
Mahmud K K
MK
Venkitaraman
Ashok R
AR
Kowalczykowski
Stephen C
SC
D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D024682:BRCA2 Protein / Q000737:chemistry / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D051135:Rad51 Recombinase / Q000378:metabolism*; D011995:Recombination, Genetic
D024682:BRCA2 Protein; D004277:DNA, Single-Stranded; D000255:Adenosine Triphosphate; D051135:Rad51 Recombinase