title: Sodium arsenite inhibits spontaneous and induced mutations in Escherichia coli.
abstract: Sodium arsenite at a non-toxic concentration was found to inhibit strongly mutagenesis induced by ultraviolet light (UV), 4-nitroquinoline-1-oxide (4NQO), furylfuramide (AF-2) and methyl methane-sulfonate (MMS) as well as spontaneous mutation in the reversion assay of E. coli WP2uvrA/pKM101. The effect was not, however, seen in the case of the mutagenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In order to elucidate the mechanism of the mutation-inhibitory effect of sodium arsenite, its action on umuC gene expression and DNA-repair systems was investigated. It was found that sodium arsenite depressed beta-galactosidase induction, corresponding to the umuC gene expression. For UV-irradiated E. coli strains possessing different DNA-repair capacities, sodium arsenite decreased the UV survival rates of WP2, WP2uvrA[uvrA] and WP67[uvrA polA], increased those of SOS-uninducible strains having either the recA+ or uvrA+ such as CM571 [recA], CM561 [lexA(Ind-)] and CM611[uvrA lexA (Ind-)], and did not affect that of the uvrA recA double mutant, WP100. From these results, we assume that sodium arsenite may have at least two roles in its antimutagenesis: as an inhibitor of umuC gene expression, and as an enhancer of the error-free repairs depending on the uvrA and recA genes.
authors.forename: T
authors.initials: T
authors.lastname: Nunoshiba
authors.forename: H
authors.initials: H
authors.lastname: Nishioka
mesh_terms: D001151:Arsenic / Q000494:pharmacology*; D018053:Arsenites; D004260:DNA Repair / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation / Q000528:radiation effects; D005798:Genes, Bacterial; D009153:Mutagens / Q000037:antagonists & inhibitors*; D009154:Mutation / Q000187:drug effects* / Q000528:radiation effects; D013014:SOS Response, Genetics / Q000187:drug effects*; D017670:Sodium Compounds; D014466:Ultraviolet Rays
chemical_list: D018053:Arsenites; D009153:Mutagens; D017670:Sodium Compounds; C017947:sodium arsenite; D001151:Arsenic