EMSY overexpression disrupts the BRCA2/RAD51 pathway in the DNA-damage response: implications for chromosomal instability/recombination syndromes as checkpoint diseases

Mol Genet Genomics. 2011 Apr;285(4):325-40. doi: 10.1007/s00438-011-0612-5. Epub 2011 Mar 16.

Abstract

EMSY links the BRCA2 pathway to sporadic breast/ovarian cancer. It encodes a nuclear protein that binds to the BRCA2 N-terminal domain implicated in chromatin/transcription regulation, but when sporadically amplified/overexpressed, increased EMSY level represses BRCA2 transactivation potential and induces chromosomal instability, mimicking the activity of BRCA2 mutations in the development of hereditary breast/ovarian cancer. In addition to chromatin/transcription regulation, EMSY may also play a role in the DNA-damage response, suggested by its ability to localize at chromatin sites of DNA damage/repair. This implies that EMSY overexpression may also repress BRCA2 in DNA-damage replication/checkpoint and recombination/repair, coordinated processes that also require its interacting proteins: PALB2, the partner and localizer of BRCA2; RPA, replication/checkpoint protein A; and RAD51, the inseparable recombination/repair enzyme. Here, using a well-characterized recombination/repair assay system, we demonstrate that a slight increase in EMSY level can indeed repress these two processes independently of transcriptional interference/repression. Since EMSY, RPA and PALB2 all bind to the same BRCA2 region, these findings further support a scenario wherein: (a) EMSY amplification may mimic BRCA2 deficiency, at least by overriding RPA and PALB2, crippling the BRCA2/RAD51 complex at DNA-damage and replication/transcription sites; and (b) BRCA2/RAD51 may coordinate these processes by employing at least EMSY, PALB2 and RPA. We extensively discuss the molecular details of how this can happen to ascertain its implications for a novel recombination mechanism apparently conceived as checkpoint rather than a DNA repair system for cell division, survival, death, and human diseases, including the tissue specificity of cancer predisposition, which may renew our thinking about targeted therapy and prevention.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • BRCA2 Protein / genetics
  • BRCA2 Protein / metabolism*
  • Cell Line, Tumor
  • Chromosomal Instability / genetics*
  • DNA Breaks, Double-Stranded
  • DNA Damage*
  • DNA Repair / genetics
  • DNA Replication / genetics
  • Humans
  • Inverted Repeat Sequences / genetics
  • Models, Biological
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Rad51 Recombinase / genetics
  • Rad51 Recombinase / metabolism*
  • Recombination, Genetic*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Signal Transduction* / genetics

Substances

  • BRCA2 Protein
  • EMSY protein, human
  • Neoplasm Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • RAD51 protein, human
  • Rad51 Recombinase