PALB2 functionally connects the breast cancer susceptibility proteins BRCA1 and BRCA2.
BRCA1 and BRCA2 are prominently associated with inherited breast and ovarian cancer. The encoded proteins function in DNA damage responses, but no functional link between BRCA1 and BRCA2 has been established. We show here that PALB2 physically and functionally connects BRCA1 and BRCA2 into a DNA damage response network that also includes the RAD51 recombinase. PALB2 directly binds BRCA1, as determined with bacterially expressed fragments of each protein. Furthermore, PALB2 independently interacts with BRCA1 and BRCA2 through its NH2 and COOH termini, respectively. Critically, two point mutants (L21P and L24P) of the PALB2 coiled-coil domain or an NH2-terminal deletion (Delta1-70) disrupt its interaction with BRCA1. We have reconstituted PALB2-deficient cells with PALB2Delta1-70, PALB2-L21P, or PALB2-L24P, or with COOH-terminally truncated PALB2 that is deficient for interaction with BRCA2. Using extracts from these cells, we find that PALB2 mediates the physical interaction of BRCA2 with a COOH-terminal fragment of BRCA1. Analysis of the assembly of foci in these cells by BRCA1, PALB2, BRCA2, and RAD51 suggests that BRCA1 recruits PALB2, which in turn organizes BRCA2 and RAD51. Resistance to mitomycin C and the repair of DNA double-strand breaks by homologous recombination require the interaction of PALB2 with both BRCA1 and BRCA2. These results suggest that BRCA1 and BRCA2 cooperate in DNA damage responses in a PALB2-dependent manner, and have important implications for the genesis of breast/ovarian cancer and for chemotherapy with DNA interstrand cross-linking agents.
Zhang
Fan
F
Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio 45229, USA.
Fan
Qiang
Q
Ren
Keqin
K
Andreassen
Paul R
PR
D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins; D019313:BRCA1 Protein / Q000378:metabolism*; D024682:BRCA2 Protein / Q000378:metabolism*; D045744:Cell Line, Tumor; D004249:DNA Damage; D000076164:Fanconi Anemia Complementation Group N Protein; D020022:Genetic Predisposition to Disease; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D051135:Rad51 Recombinase / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C118024:BLID protein, human; D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D000076164:Fanconi Anemia Complementation Group N Protein; D009687:Nuclear Proteins; C512790:PALB2 protein, human; D025521:Tumor Suppressor Proteins; C495153:RAD51 protein, human; D051135:Rad51 Recombinase