TOPORS modulates H2AX discriminating genotoxic stresses

J Biochem Mol Toxicol. 2012 Nov;26(11):429-38. doi: 10.1002/jbt.21438. Epub 2012 Sep 12.

Abstract

H2AX plays an important role in chromatin reorganization implicated in DNA repair and apoptosis under various DNA damaging conditions. In this study, the interaction between TOPORS (topoisomerase I-binding protein) and H2AX was verified using mammalian cell extracts exposed to diverse DNA damaging stresses such as ionizing radiation, doxorubicin, camptothecin, and hydrogen peroxide. In vitro assays for ubiquitination revealed that TOPORS functions as a novel E3 ligase for H2AX ubiquitination. TOPORS was found to be dissociated from H2AX proteins when cells were exposed to oxidative stress, but not replication-inducing DNA damaging stress. The protein stability of H2AX was decreased when TOPORS was ectopically expressed in cells, and oxidative stresses such as hydrogen peroxide and ionizing radiation induced recovery of the H2AX protein level. Therefore, these biochemical data suggest that TOPORS plays a key role in the turnover of H2AX protein, discriminating the type of DNA damaging stress.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Camptothecin / pharmacology
  • Cell Line
  • Chromatin* / drug effects
  • Chromatin* / radiation effects
  • DNA Breaks, Double-Stranded* / drug effects
  • DNA Breaks, Double-Stranded* / radiation effects
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Doxorubicin / pharmacology
  • Gamma Rays / adverse effects
  • HEK293 Cells
  • Histones / genetics
  • Histones / metabolism*
  • Humans
  • Hydrogen Peroxide / pharmacology
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Oxidants / pharmacology
  • Oxidative Stress* / drug effects
  • Oxidative Stress* / radiation effects
  • Protein Stability / drug effects
  • Protein Stability / radiation effects
  • Recombinant Fusion Proteins / metabolism
  • Sumoylation / drug effects
  • Sumoylation / radiation effects
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination* / drug effects
  • Ubiquitination* / radiation effects

Substances

  • Antineoplastic Agents
  • Chromatin
  • DNA-Binding Proteins
  • H2AX protein, human
  • Histones
  • Neoplasm Proteins
  • Nuclear Proteins
  • Oxidants
  • Recombinant Fusion Proteins
  • Doxorubicin
  • Hydrogen Peroxide
  • TOPORS protein, human
  • Ubiquitin-Protein Ligases
  • Camptothecin