title: Differences in DNA damage induced by mutagenic and nonmutagenic 4-aminoazobenzene derivatives in Escherichia coli.
abstract: DNA lesions produced in Escherichia coli AB2500 (uvrA) exposed to the carcinogen N-hydroxy-3-methoxy-4-aminoazobenzene (N-OH-3-MeO-AAB) or the noncarcinogen N-hydroxy-2-methoxy-4-aminoazobenzene (N-OH-2-MeO-AAB) were investigated by alkaline sucrose gradient sedimentation and 32P-postlabeling analysis. Alkali-labile sites appeared to be formed equally in cells treated with both aminoazobenzene derivatives. 32P-Postlabeling analysis revealed that the 3-MeO-AAB-DNA adduct level was 25-fold higher than that for 2-MeO-AAB-DNA adducts. In addition to major adducts, 4 minor spots were detected in N-OH-3-MeO-AAB-treated cells, while only one major adduct was found in N-OH-2-MeO-AAB-treated cells. The mutagenicities and cytotoxicities were also determined with E. coli with different repair capacities; we found that repair of 3-MeO-AAB damages is strongly dependent on the UVR repair system. Moreover, N-OH-3-MeO-AAB, but not N-OH-2-MeO-AAB, could induce recA and umuC gene expression, which was higher in uvrA strains than in the wild type.
authors.affiliation: Laboratory of Biochemistry, Aichi Cancer Center Research Institute, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kojima
authors.forename: T
authors.initials: T
authors.lastname: Morita
authors.forename: M
authors.initials: M
authors.lastname: Degawa
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: M
authors.initials: M
authors.lastname: Tada
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D004269:DNA, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006898:Hydroxylamines / Q000633:toxicity*; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity; D011938:Rec A Recombinases / Q000235:genetics; D010128:p-Aminoazobenzene / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D001426:Bacterial Proteins; D002273:Carcinogens; D004269:DNA, Bacterial; D006898:Hydroxylamines; D009153:Mutagens; D010128:p-Aminoazobenzene; C074621:N-hydroxy-2-methoxy-4-(phenylazo)-benzenamine; C074620:N-hydroxy-3-methoxy-4-(phenylazo)-benzenamine; D011938:Rec A Recombinases