A Class of Environmental and Endogenous Toxins Induces BRCA2 Haploinsufficiency and Genome Instability

Cell. 2017 Jun 1;169(6):1105-1118.e15. doi: 10.1016/j.cell.2017.05.010.


Mutations truncating a single copy of the tumor suppressor, BRCA2, cause cancer susceptibility. In cells bearing such heterozygous mutations, we find that a cellular metabolite and ubiquitous environmental toxin, formaldehyde, stalls and destabilizes DNA replication forks, engendering structural chromosomal aberrations. Formaldehyde selectively depletes BRCA2 via proteasomal degradation, a mechanism of toxicity that affects very few additional cellular proteins. Heterozygous BRCA2 truncations, by lowering pre-existing BRCA2 expression, sensitize to BRCA2 haploinsufficiency induced by transient exposure to natural concentrations of formaldehyde. Acetaldehyde, an alcohol catabolite detoxified by ALDH2, precipitates similar effects. Ribonuclease H1 ameliorates replication fork instability and chromosomal aberrations provoked by aldehyde-induced BRCA2 haploinsufficiency, suggesting that BRCA2 inactivation triggers spontaneous mutagenesis during DNA replication via aberrant RNA-DNA hybrids (R-loops). These findings suggest a model wherein carcinogenesis in BRCA2 mutation carriers can be incited by compounds found pervasively in the environment and generated endogenously in certain tissues with implications for public health.

Keywords: BRCA2; R-loop; SWATH-MS; acetaldehyde; aldehyde; formaldehyde; induced haploinsufficiency; proteasomal degradation; replication stress.

MeSH terms

  • BRCA2 Protein / genetics*
  • Chromosome Aberrations / drug effects*
  • DNA Damage
  • DNA Replication / drug effects
  • DNA-Binding Proteins / metabolism
  • Formaldehyde / toxicity*
  • Genomic Instability / drug effects*
  • Haploinsufficiency
  • HeLa Cells
  • Humans
  • MRE11 Homologue Protein
  • Proteome
  • Ribonuclease H / metabolism
  • Toxins, Biological / toxicity*


  • BRCA2 Protein
  • BRCA2 protein, human
  • DNA-Binding Proteins
  • MRE11 protein, human
  • Proteome
  • Toxins, Biological
  • Formaldehyde
  • MRE11 Homologue Protein
  • Ribonuclease H
  • ribonuclease HI