Mismatch repair proteins recruit DNA methyltransferase 1 to sites of oxidative DNA damage

J Mol Cell Biol. 2016 Jun;8(3):244-54. doi: 10.1093/jmcb/mjv050. Epub 2015 Jul 17.

Abstract

At sites of chronic inflammation, epithelial cells are exposed to high levels of reactive oxygen species and undergo cancer-associated DNA methylation changes, suggesting that inflammation may initiate epigenetic alterations. Previously, we demonstrated that oxidative damage causes epigenetic silencing proteins to become part of a large complex that is localized to GC-rich regions of the genome, including promoter CpG islands that are epigenetically silenced in cancer. However, whether these proteins were recruited directly to damaged DNA or during the DNA repair process was unknown. Here we demonstrate that the mismatch repair protein heterodimer MSH2-MSH6 participates in the oxidative damage-induced recruitment of DNA methyltransferase 1 (DNMT1) to chromatin. Hydrogen peroxide treatment induces the interaction of MSH2-MSH6 with DNMT1, suggesting that the recruitment is through a protein-protein interaction. Importantly, the reduction in transcription for genes with CpG island-containing promoters caused by oxidative damage is abrogated by knockdown of MSH6 and/or DNMT1. Our findings provide evidence that the role of DNMT1 at sites of oxidative damage is to reduce transcription, potentially preventing transcription from interfering with the repair process. This study uniquely brings together several factors that are known to contribute to colon cancer, namely inflammation, mismatch repair proteins, and epigenetic changes.

Keywords: DNA repair; DNMT1; SIRT1; epigenetics; mismatch repair; oxidative damage; transcription.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line, Tumor
  • Chromatin / metabolism
  • CpG Islands
  • DNA (Cytosine-5-)-Methyltransferases / metabolism*
  • DNA Damage*
  • DNA Mismatch Repair* / drug effects
  • DNA Mismatch Repair* / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Knockdown Techniques
  • Humans
  • Hydrogen Peroxide / pharmacology
  • MutS Homolog 2 Protein / metabolism
  • Oxidation-Reduction / drug effects
  • Proliferating Cell Nuclear Antigen / metabolism
  • Promoter Regions, Genetic
  • Protein Binding / drug effects
  • Transcription, Genetic / drug effects

Substances

  • Chromatin
  • DNA-Binding Proteins
  • G-T mismatch-binding protein
  • Proliferating Cell Nuclear Antigen
  • Hydrogen Peroxide
  • DNA (Cytosine-5-)-Methyltransferases
  • MSH2 protein, human
  • MutS Homolog 2 Protein