Cancer-predisposing mutations within the RING domain of BRCA1: loss of ubiquitin protein ligase activity and protection from radiation hypersensitivity

Proc Natl Acad Sci U S A. 2001 Apr 24;98(9):5134-9. doi: 10.1073/pnas.081068398.


BRCA1 is a breast and ovarian cancer-specific tumor suppressor that seems to be involved in transcription and DNA repair. Here we report that BRCA1 exhibits a bona fide ubiquitin (Ub) protein ligase (E3) activity, and that cancer-predisposing mutations within the BRCA1 RING domain abolish its Ub ligase activity. Furthermore, these mutants are unable to reverse gamma-radiation hypersensitivity of BRCA1-null human breast cancer cells, HCC1937. Additionally, these mutations within the BRCA1 RING domain are not capable of restoring a G(2) + M checkpoint in HCC1937 cells. These results establish a link between Ub protein ligase activity and gamma-radiation protection function of BRCA1, and provide an explanation for why mutations within the BRCA1 RING domain predispose to cancer. Furthermore, we propose that the analysis of the Ub ligase activity of RING-domain mutations identified in patients may constitute an assay to predict predisposition to cancer.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • BRCA1 Protein / chemistry*
  • BRCA1 Protein / genetics
  • BRCA1 Protein / metabolism*
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Cell Cycle / radiation effects
  • Female
  • Gamma Rays
  • Humans
  • Ligases / chemistry*
  • Ligases / genetics
  • Ligases / metabolism*
  • Molecular Sequence Data
  • Mutation / genetics*
  • Protein Structure, Tertiary
  • Radiation Tolerance / genetics*
  • Tumor Cells, Cultured
  • Ubiquitin-Protein Ligases


  • BRCA1 Protein
  • Ubiquitin-Protein Ligases
  • Ligases