title: Inhibitory effect of cadmium and mercury ions on induction of the adaptive response in Escherichia coli.
abstract: Cadmium and mercury ions inhibited the promotion of ada and alkA gene expression in the adaptive process induced by methylating agents such as N-methyl-N-nitrosourea (MNU), methyl methanesulfonate (MMS) and methyl iodide in Escherichia coli. In fact, the induction of O6-methylguanine-DNA methyl-transferase (MGTase) by MNU was suppressed in E. coli in the presence of these metal ions. These ions potentiated mutagenesis induced by methylating agents such as MNU and MMS, but not that induced by ethylating agents, UV irradiation, or N4-aminocytidine. These comutagenic effects were observed in wild-type and umuC36 strains of E. coli but not in the ada-5 strain, which is unable to induce the adaptive response. These results suggest that the comutagenic effects of Cd2+ and Hg2+ are due to inhibition of ada and alkA gene expression promoted by methylated MGTase.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Imaeda
authors.forename: Y
authors.initials: Y
authors.lastname: Kawazoe
mesh_terms: D002104:Cadmium / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006847:Hydrocarbons, Iodinated / Q000494:pharmacology; D008628:Mercury / Q000494:pharmacology*; D008745:Methylation; D008770:Methylnitrosourea / Q000494:pharmacology; D008780:Methyltransferases / Q000096:biosynthesis / Q000235:genetics*; D016296:Mutagenesis; D019853:O(6)-Methylguanine-DNA Methyltransferase; D014466:Ultraviolet Rays
chemical_list: D006847:Hydrocarbons, Iodinated; D002104:Cadmium; D008770:Methylnitrosourea; C014055:methyl iodide; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D008628:Mercury