title: Mutation spectra of N-ethyl-N'-nitro-N-nitrosoguanidine and 1-(2-hydroxyethyl)-1-nitrosourea in Escherichia coli.
abstract: DNA sequencing was used to determine the specific types of DNA base changes induced following in vivo exposure of Escherichia coli to the ethylating agent N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) and the hydroxyethylating agent 1-(2-hydroxyethyl)-1-nitrosourea (HENU) using the xanthine guanine phosphoribosyltransferase (gpt) gene as the genetic target. We observed that 22/30 of the ENNG-induced mutations were GC----AT transitions, 4/30 were AT----GC transitions, 3/30 were AT----TA transversions, and 1/30 was an AT----CG transversion. We observed that 37/40 HENU-induced mutations were GC----AT transitions and that the remaining 3/40 were AT----GC transitions. A majority of the GC----AT transitions induced by ENNG and HENU (68% and 73%, respectively) occurred at the second guanine of the sequence 5'-GG(A or T)-3'; this sequence specificity was similar to that previously seen with the alkylating agents N-methyl- and N-ethyl-N-nitrosourea (MNU and ENU) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). A DNA strand preference for the G----A changes (antisense strand), previously noted for MNU, ENU, and MNNG, was observed following exposure to HENU and ENNG. The AT----GC transitions induced by ENNG, HENU, and ENU also exhibit a sequence specificity with 13/13 mutations occurring at the T of the sequence 5'-NTC-3'. A strand preference was not apparent for these mutations.
authors.affiliation: Cellular and Molecular Toxicology Department, Chemical Industry Institute of Toxicology, Research Triangle Park, NC 27709.
authors.forename: K K
authors.initials: KK
authors.lastname: Richardson
authors.forename: R M
authors.initials: RM
authors.lastname: Crosby
authors.forename: T R
authors.initials: TR
authors.lastname: Skopek
mesh_terms: D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D005038:Ethylnitrosourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D005798:Genes, Bacterial / Q000187:drug effects; D008769:Methylnitronitrosoguanidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010957:Plasmids
chemical_list: D004269:DNA, Bacterial; D008769:Methylnitronitrosoguanidine; C022146:1-(2-hydroxyethyl)-1-nitrosourea; C013525:ENNG; D005038:Ethylnitrosourea