title: 1-Nitropyrene efficiently induces mitotic recombination in Saccharomyces cerevisiae.
abstract: Nitropyrene, a mutagenic and carcinogenic component of diesel exhaust, has been shown to be a potent bacterial and mammalian mutagen. There is, however, some controversy regarding the genotoxic effects of 1-nitropyrene towards yeast. To obtain insights into the mechanisms of 1-nitropyrene-induced mutations in Saccharomyces cerevisiae, we have attempted to characterize the genetic alterations that inactivate the endogenous CAN1 gene either in haploid cells or in heterozygous diploid cells. 1-Nitropyrene, without any activation treatment, showed a substantial toxic effect until 500 microM. The mutation frequency in haploid cells treated with 500 microM of 1-nitropyrene was 1.59 x 10(-5), which is 15-fold higher than the control value. Sequencing of mutants indicated that both frameshifts and base substitutions were increased. In diploid cells treated with 500 microM of 1-nitropyrene, the frequency with which can1Delta::LEU2/can1Delta::LEU2 was converted from CAN1/can1Delta::LEU2, a phenotypic change from a canavanine-sensitive to canavanine-resistant form, was 8.59 x 10(-4), which is 9.15-fold higher than the spontaneous level. More than 99% of the 1-nitropyrene-induced mutations in canavanine-resistant diploid cells constituted a gene conversion or crossover. Chromosome loss was not increased after treatment with 1-nitropyrene. These results suggest that 1-nitropyrene is an agent that efficiently induces point mutations, gene conversion, and crossover, but not chromosome loss, in S. cerevisiae.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
authors.forename: Lalla Rajaa
authors.initials: LR
authors.lastname: Rhenimi
authors.forename: Naglaa Fathi
authors.initials: NF
authors.lastname: Abu-Nasr
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D050256:Antimitotic Agents / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D008938:Mitosis / Q000187:drug effects / Q000235:genetics*; D009153:Mutagens / Q000008:administration & dosage*; D011721:Pyrenes / Q000008:administration & dosage*; D011995:Recombination, Genetic / Q000235:genetics* / Q000528:radiation effects; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics*
chemical_list: D050256:Antimitotic Agents; D009153:Mutagens; D011721:Pyrenes; C032668:1-nitropyrene