DEVELOPMENT OF NEW TESTER STRAINS DERIVED FROM ESCHERICHIA-COLI WP2 UVRA FOR THE DETERMINATION OF MUTATIONAL SPECIFICITY

We have developed a set of multipurpose tester strains (WP3101 to WP31 06) derived from E. coli WP2uvrA for the detection and classification of mutagens. Six kinds of F' plasmid (lacI, lacZ, proAB(+)) in strains CC101-CC106, each of which carried a different lacZ allele, were tran sferred to a Delta(lac-pro) derivative of WP2uvrA. Assays for transiti ons and transversions are based upon Lac(+) reversion of a specific mu tation located within the lacZ gene on an F' plasmid in strains WP3101 -WP3106. In addition, the trpE65(ochre) allele in the same strains is available for Trp(+) reversion assays. Using the new tester strains, w e investigated the mutational specificities of various chemical mutage ns. Base analog mutagens and alkylating mutagens induced specific type s of base substitutions. G:C --> A:T transitions and G:C --> T:A trans versions predominated in mutagenesis induced by 4-nitroquinoline 1-oxi de. Only a slight increase in G:C --> T:A transversions was observed i n cells treated with 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamid (AF-2), although the potent mutagenicity of AF-2 was detected in a concurrent Trp(+) reversion assay in the same strain. Sodium azide, on the other hand, was negative in the Trp(+) reversion assay but specifically indu ced G:C --> A:T transitions. Present finding suggested that target sit es for AF-2- and azide-induced lesions may largely depend on sequence context. (C) 1998 Elsevier Science B.V.