53BP1 inhibits homologous recombination in brca1-deficient cells by blocking resection of DNA breaks

Samuel F. Bunting, Elsa Callén, Nancy Wong, Hua Tang Chen, Federica Polato, Amanda Gunn, Anne Bothmer, Niklas Feldhahn, Oscar Fernandez-Capetillo, Liu Cao, Xiaoling Xu, Chu Xia Deng, Toren Finkel, Michel Nussenzweig, Jeremy M. Stark, André Nussenzweig

Research output: Contribution to journalArticlepeer-review

1001 Scopus citations


Defective DNA repair by homologous recombination (HR) is thought to be a major contributor to tumorigenesis in individuals carrying Brca1 mutations. Here, we show that DNA breaks in Brca1-deficient cells are aberrantly joined into complex chromosome rearrangements by a process dependent on the nonhomologous end-joining (NHEJ) factors 53BP1 and DNA ligase 4. Loss of 53BP1 alleviates hypersensitivity of Brca1 mutant cells to PARP inhibition and restores error-free repair by HR. Mechanistically, 53BP1 deletion promotes ATM-dependent processing of broken DNA ends to produce recombinogenic single-stranded DNA competent for HR. In contrast, Lig4 deficiency does not rescue the HR defect in Brca1 mutant cells but prevents the joining of chromatid breaks into chromosome rearrangements. Our results illustrate that HR and NHEJ compete to process DNA breaks that arise during DNA replication and that shifting the balance between these pathways can be exploited to selectively protect or kill cells harboring Brca1 mutations.

Original languageEnglish (US)
Pages (from-to)243-254
Number of pages12
Issue number2
StatePublished - Apr 2010
Externally publishedYes


  • DNA
  • Humdisease

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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