title: Escherichia coli BTC, a human cytochrome P450 competent tester strain with a high sensitivity towards alkylating agents: involvement of alkyltransferases in the repair of DNA damage induced by aromatic amines.
abstract: We report here on strain BTC, a new Escherichia coli mutagenicity tester strain for the expression of human cytochrome P450 (CYP) with an enhanced sensitivity for the detection of alkylating agents. This strain was developed first through knocking out of the genes ada and ogt in our previously developed strain BMX100, resulting in PD1000. Strain PD1000 demonstrated a significantly higher detection sensitivity towards several alkylating agents such as N-nitrosodiethylamine (NNdEA), N-nitrosodi-n-propylamine (NNdPA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Unexpectedly, this strain also showed an enhanced sensitivity towards 2-aminoanthracene (2AA), 4-aminobiphenyl (4AbPh), 2-aminofluorene (2AF) and 2-nitroanthracene (2NA) mutagenicity. Subsequently, our previously developed bi-plasmid system for the co-expression of a specific human CYP form (CYP1A2, 2A6 or 2E1) with human NADPH-cytochrome P450 reductase (RED) was introduced in strain PD1000, resulting in strains BTC1A2, BTC2A6 and BTC2E1, respectively. The mutagenicity of NNdEA and NNK was successfully detected with strains BTC2A6 and BTC2E1 and with strains BTC1A2 and BTC2A6, respectively, in contrast to the corresponding MTC (ada+ ogt+) CYP strains. The (ada- ogt-) deficient strain BTC1A2 also showed an enhanced sensitivity towards the detection of 2AA mutagenicity, when compared with the proficient repair strain MTC1A2. This enhancement was much more pronounced with strain PD1000 using the rat liver S9 fraction than with strain BTC1A2.
authors.affiliation: Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal.
authors.forename: Maria Paula
authors.initials: MP
authors.lastname: Duarte
authors.forename: Bernardo Brito
authors.initials: BB
authors.lastname: Palma
authors.forename: António
authors.initials: A
authors.lastname: Laires
authors.forename: José Santos
authors.initials: JS
authors.lastname: Oliveira
authors.forename: José
authors.initials: J
authors.lastname: Rueff
authors.forename: Michel
authors.initials: M
authors.lastname: Kranendonk
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000378:metabolism*; D000477:Alkylating Agents / Q000633:toxicity*; D000588:Amines / Q000633:toxicity*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D004260:DNA Repair; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D006801:Humans; D008099:Liver / Q000187:drug effects; D008780:Methyltransferases / Q000235:genetics; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics; D051381:Rats
chemical_list: C086794:Ada-C protein, E coli; D000477:Alkylating Agents; D000588:Amines; D029968:Escherichia coli Proteins; D009153:Mutagens; D010446:Peptide Fragments; D004247:DNA; D001189:Aryl Hydrocarbon Hydroxylases; D009251:NADPH-Ferrihemoprotein Reductase; D008780:Methyltransferases; C067511:Ogt protein, E coli; D019883:Alkyl and Aryl Transferases; C050956:DNA alkyltransferase