Salmonella typhimurium strain TA100 differentiates several classes of carcinogens and mutagens by base substitution specificity.
The mutational specificity of N-methylnitrosourea (MNU), nitrosoguanidine (MNNG), methyl methanesulfonate (MMS), sodium azide (NaN3), 4-nitroquinoline oxide (4NQO), benzo[a]pyrene (BP), nitrofurantoin (NF), aflatoxin B1 (AFB1), adriamycin (ADM) and UVA-activated angelicin in Salmonella typhimurium strain TA100 has been examined using allele-specific oligonucleotide hybridization and DNA sequence analyses. These ten mutagens produced five unique classes of reversion spectra, distinct from spontaneous, or the previously characterized 5-azacytidine, ultraviolet light (UV), 8-methoxypsoralen plus UVA (PUVA) and 60Co-induced mutation spectra. For example, 90% of MNU and MNNG-induced mutations in strain TA100 revertants were G:C-->A:T transitions with the majority (82%) occurring in the first position of the CCC codon. In contrast, NaN3 preferentially induced G:C-->A:T transitions at the second codon position (78%). Although MMS, NQO, BP, NF, ADM and AFB1 induced primarily G:C-->T:A transversions (73-86%), these mutagens fall into two classes based on site preference: NF and AFB1 yielded almost exclusively position two transversions (69-78%) whereas ADM, NQO, BP and MMS exhibited a two-fold preference for site 2 over site 1 (on average 52% versus 22%). Angelicin photomutagenesis resulted in the recovery of G:C-->A:T and G:C-->T:A mutations at both codon positions in roughly equal proportions (approximately 20-25% each). Approximately 1% of the mutagen-induced revertants occurred via extragenic tRNA suppressor mutations, while 1% were multiple (usually tandem double) base substitutions. Ultraviolet mutagenesis experiments demonstrated that tandem base substitutions are promoted by pKM101-encoded mucAB gene products. A comparison of the mutagenic specificity derived for several carcinogens in hisG46 with the responses of several eukaryotic gene targets (e.g. HPRT, aprt, supF) revealed a high concordance between these targets. Thus, the Salmonella hisG46 locus provides a rapid, simple system for determining base substitution specificity and for studying mechanisms of mutagenesis.
Koch
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Molecular Biology Branch, Food and Drug Administration, Washington, DC 20204.
Henrikson
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Kupchella
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Cebula
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TA
D000483:Alleles; D001482:Base Composition; D001483:Base Sequence; D002273:Carcinogens / Q000633:toxicity*; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics; D008969:Molecular Sequence Data; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation / Q000235:genetics* / Q000502:physiology; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics*; D012680:Sensitivity and Specificity
D002273:Carcinogens; D004269:DNA, Bacterial; D009153:Mutagens