title: Frameshift mutagenesis in bacteria by 8-methoxypsoralen (methoxalen) in the dark.
abstract: We confirm that 8-methoxypsoralen (8-MOP) in the dark induces frameshift mutations in both Escherichia coli and Salmonella typhimurium when present in adequate concentration under growth conditions. The dose response is sigmoidal with a threshold or quasi-threshold at concentrations below about 10 microgram/ml. Frameshift mutagenesis by 8-MOP in the dark is unaffected by mutations at the uvrA or uvrB genes, in contrast to base pair substitution mutagenesis by 8-MOP plus near UV light. RecA (but not recB) bacteria are hypersensitive to the growth-inhibiting action of 8-MOP in the dark and are not detectably mutagenized. The characteristics of 8-MOP dark mutagenesis are consistent with the chemical interacting in a non-covalent manner with DNA and affecting the rate of occurrence of base deletions or insertions during DNA replication. The question of extrapolation of the genetic effect of 8-MOP to man is discussed.
mesh_terms: D003624:Darkness; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects*; D005815:Genetic Code; D008730:Methoxsalen / Q000494:pharmacology*; D009153:Mutagens; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic; D012486:Salmonella typhimurium / Q000187:drug effects*; D014158:Transcription, Genetic
chemical_list: D009153:Mutagens; D008730:Methoxsalen