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  • Title: Differences in DNA damage induced by mutagenic and nonmutagenic 4-aminoazobenzene derivatives in Escherichia coli.
    Author: Kojima M, Morita T, Degawa M, Hashimoto Y, Tada M.
    Journal: Mutat Res; 1992 Jun; 274(1):65-71. PubMed ID: 1375333.
    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.
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