title: Repair of DNA lesions induced by hydrogen peroxide in the presence of iron chelators in Escherichia coli: participation of endonuclease IV and Fpg.
abstract: In Escherichia coli, the repair of lethal DNA damage induced by H(2)O(2) requires exonuclease III, the xthA gene product. Here, we report that both endonuclease IV (the nfo gene product) and exonuclease III can mediate the repair of lesions induced by H(2)O(2) under low-iron conditions. Neither the xthA nor the nfo mutants was sensitive to H(2)O(2) in the presence of iron chelators, while the xthA nfo double mutant was significantly sensitive to this treatment, suggesting that both exonuclease III and endonuclease IV can mediate the repair of DNA lesions formed under such conditions. Sedimentation studies in alkaline sucrose gradients also demonstrated that both xthA and nfo mutants, but not the xthA nfo double mutant, can carry out complete repair of DNA strand breaks and alkali-labile bonds generated by H(2)O(2) under low-iron conditions. We also found indications that the formation of substrates for exonuclease III and endonuclease IV is mediated by the Fpg DNA glycosylase, as suggested by experiments in which the fpg mutation increased the level of cell survival, as well as repair of DNA strand breaks, in an AP endonuclease-null background.
authors.affiliation: Laboratório de Radiobiologia Molecular, Programa de Biologia Molecular, Instituto de Biofisica Carlos Chagas Filho, Centro de Ciências da Saúde-Bloco G, Universidade Federal do Rio de Janeiro, CEP 21949-900 Rio de Janeiro, RJ, Brazil.
authors.forename: R S
authors.initials: RS
authors.lastname: Galhardo
authors.forename: C E
authors.initials: CE
authors.lastname: Almeida
authors.forename: A C
authors.initials: AC
authors.lastname: Leitão
authors.forename: J B
authors.initials: JB
authors.lastname: Cabral-Neto
mesh_terms: D015082:2,2'-Dipyridyl / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019757:Carbon-Oxygen Lyases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D016680:Genome, Bacterial; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology*; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007502:Iron Chelating Agents; D015082:2,2'-Dipyridyl; D006861:Hydrogen Peroxide; D007501:Iron; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase