'Rec-lac test' for detecting SOS-inducing activity of environmental genotoxic substance.
beta-Galactosidase activities (beta-GA) of E. coli strains carrying the fusion gene of recA and lacZ, GE94 and its DNA repair-deficient derivatives such as KY946[uvrA], KY945[recA] and KY943[lexA] treated with UV, 4NQO, MNNG and MMC were examined. The beta-GA, reflecting the SOS-inducing activity, of GE94 and KY946 treated with these compounds increased significantly with a clear dose-response relationship, and reached a maximum level within 60 min, while no response was seen in KY945 and KY943. Using KY946 and KY945 as a positive and a negative indicator, respectively, the SOS-inducing activity of oxidative mutagens, i.e., hydrogen peroxide (H2O2), formaldehyde, tert-butyl hydroperoxide, cumene hydroperoxide and streptonigrin, was investigated. Clear dose-dependent increases in beta-GA were observed in KY946 treated with all oxidative mutagens tested, but not in KY945. Significant increases in beta-GA were observed with a lower concentration of H2O2 and a shorter incubation time of 4NQO in this assay than in the umu-test. The assay, called 'Rec-lac test' by us, may be useful to detect environmental genotoxic substances.
Nunoshiba
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Division of Biochemistry, Doshisha University, Kyoto, Japan.
Nishioka
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D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity; D000477:Alkylating Agents; D003001:Cloning, Molecular; D004260:DNA Repair; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D005798:Genes, Bacterial; D007700:Kinetics; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D016685:Mitomycin; D008937:Mitomycins / Q000633:toxicity; D009152:Mutagenicity Tests; D009153:Mutagens; D010084:Oxidation-Reduction; D011938:Rec A Recombinases / Q000235:genetics*; D013014:SOS Response, Genetics; D014466:Ultraviolet Rays; D001616:beta-Galactosidase / Q000096:biosynthesis
D000477:Alkylating Agents; D008937:Mitomycins; D009153:Mutagens; D008769:Methylnitronitrosoguanidine; D016685:Mitomycin; D015112:4-Nitroquinoline-1-oxide; D011938:Rec A Recombinases; D001616:beta-Galactosidase