title: 3'-blocking damage of DNA as a mutagenic lesion caused by hydrogen peroxide in Escherichia coli.
abstract: Ionizing radiation and hydrogen peroxide (H2O2) produce many types of oxidative DNA damage such as strand breaks, apurinic/apyrimidinic (AP) sites, base modifications and 3'-blocking damage such as 3'-phosphoglycolated and 3'-phosphorylated termini. AP sites and 3'-blocking damage are repairable by exonuclease III and endonuclease IV in Escherichia coli. XthA-nfo double mutants of E. coli, which are deficient in exonuclease III and endonuclease IV, were highly sensitive to lethal and mutagenic effects of H2O2, compared with the wild-type strains. The pNT180 and pNT186 plasmids containing wild-type nfo and mutant nfo-186 gene, respectively, were introduced into the xthA-nfo mutant. The nfo-186 gene product, Nfo186, retained normal AP endonuclease activity but could not remove 3'-blocking damage from DNA. The pNT180 corrected the sensitivity of the xthA-nfo mutant to lethal and mutagenic effects of H2O2. On the other hand, the pNT186 did not have any complementation effects. From these results it was concluded that 3'-blocking damage rather than an AP site is the primary lesion responsible for both lethal and mutagenic effects of H2O2.
authors.affiliation: Laboratory of Radiation Biology, Graduate School of Science, Kyoto University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takemoto
authors.forename: Q M
authors.initials: QM
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Mito
authors.forename: T
authors.initials: T
authors.lastname: Izumi
authors.forename: H
authors.initials: H
authors.lastname: Ikehata
authors.forename: S
authors.initials: S
authors.lastname: Yonei
mesh_terms: D004249:DNA Damage; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D006861:Hydrogen Peroxide / Q000633:toxicity*; D009154:Mutation
chemical_list: D006861:Hydrogen Peroxide