title: Induction of the SOS system in a dam-3 mutant: a diagnostic strain for chemicals causing DNA mismatches.
abstract: We have developed a strain of E. coli in which expression of the SOS function sfiA, monitored by means of a sfiA::lacZ operon fusion, is efficiently triggered by the two base analogues 2-aminopurine and 5-bromo-2'-deoxyuridine. This strain resulted from introduction of a dam-3 mutation into a Uvr+, Rfa+ derivative of strain PQ37 used in the SOS chromotest, a bacterial colorimetric assay for genotoxins (Quillardet et al., 1982). The dam-3 mutation affects the mismatch correction system in E. coli. We show that the SOS-inducing capacity of a weak SOS inducer such as the alkylating agent ethyl methanesulfonate was also increased in the dam-3 strain. We provide evidence that the increase in SOS inducibility due to the dam-3 mutation is specific for compounds causing DNA mismatches and propose the use of the dam-3 derivative of PQ37 as a diagnostic strain for such agents. This diagnostic strain can be a useful addition to the SOS chromotest.
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology*; D000225:Adenine / Q000031:analogs & derivatives*; D001426:Bacterial Proteins / Q000096:biosynthesis; D001973:Bromodeoxyuridine / Q000494:pharmacology*; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D004269:DNA, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D005798:Genes, Bacterial; D008780:Methyltransferases / Q000235:genetics*; D009152:Mutagenicity Tests; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013014:SOS Response, Genetics / Q000187:drug effects*; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; D015075:2-Aminopurine; D005020:Ethyl Methanesulfonate; D008780:Methyltransferases; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D001973:Bromodeoxyuridine; D000225:Adenine