Repair versus Checkpoint Functions of BRCA1 Are Differentially Regulated by Site of Chromatin Binding.
The product of the Brca1 tumor-suppressor gene is involved in multiple aspects of the cellular DNA damage response (DDR), including activation of cell-cycle arrests and DNA double-stranded break (DSB) repair by homologous recombination. Prior reports demonstrated that BRCA1 recruitment to areas of DNA breakage depended on RAP80 and the RNF8/RNF168 E3 ubiquitin ligases. Here, we extend these findings by showing that RAP80 is only required for the binding of BRCA1 to regions flanking the DSB, whereas BRCA1 binding directly to DNA breaks requires Nijmegen breakage syndrome 1 (NBS1). These differential recruitment mechanisms differentially affect BRCA1 functions: (i) RAP80-dependent recruitment of BRCA1 to chromatin flanking DNA breaks is required for BRCA1 phosphorylation at serine 1387 and 1423 by ATM and, consequently, for the activation of S and G(2) checkpoints; and (ii) BRCA1 interaction with NBS1 upon DSB induction results in an NBS1-dependent recruitment of BRCA1 directly to the DNA break and is required for nonhomologous end-joining repair. Together, these findings illustrate that spatially distinct fractions of BRCA1 exist at the DSB site, which are recruited by different mechanisms and execute different functions in the DDR.
Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina.
Michael
M
Goldstein
Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina. michael.kastan@duke.edu.
Michael B
MB
Kastan
D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D019398:Genes, BRCA1; D018816:Genes, cdc; D006367:HeLa Cells; D056488:Histone Chaperones; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints / Q000235:genetics; D061986:MCF-7 Cells; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D059807:S Phase Cell Cycle Checkpoints / Q000235:genetics; D044767:Ubiquitin-Protein Ligases
D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; C112156:NBN protein, human; D009687:Nuclear Proteins; C486521:RNF8 protein, human; C466234:UIMC1 protein, human; D044767:Ubiquitin-Protein Ligases