title: Both replication bypass fidelity and repair efficiency influence the yield of mutations per target dose in intact mammalian cells induced by benzo[a]pyrene-diol-epoxide and dibenzo[a,l]pyrene-diol-epoxide.
abstract: Mutations induced by polycyclic aromatic hydrocarbons (PAH) are expected to be produced when error-prone DNA replication occurs across unrepaired DNA lesions formed by reactive PAH metabolites such as diol epoxides. The mutagenicity of the two PAH-diol epoxides (+)-anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and (+/-)-anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DBPDE) was compared in nucleotide excision repair (NER) proficient and deficient hamster cell lines. We applied the (32)P-postlabelling assay to analyze adduct levels and the hprt gene mutation assay for monitoring mutations. It was found that the mutagenicity per target dose was 4 times higher for DBPDE compared to BPDE in NER proficient cells while in NER deficient cells, the mutagenicity per target dose was 1.4 times higher for BPDE. In order to investigate to what extent the mutagenicity of the different adducts in NER proficient cells was influenced by repair or replication bypass, we measured the overall NER incision rate, the rate of adduct removal, the rate of replication bypass and the frequency of induced recombination in the hprt gene. The results suggest that NER of BPDE lesions are 5 times more efficient than for DBPDE lesions, in NER proficient cells. However, DBPDE adducts block replication more efficiently and also induce 6 times more recombination events in the hprt gene than adducts of BPDE, suggesting that DBPDE adducts are, to a larger extent, bypassed by homologous recombination. The results obtained here indicate that the mutagenicity of PAH is influenced not only by NER, but also by replication bypass fidelity. This has been postulated earlier based on results using in vitro enzyme assays, but is now also being recognized in terms of forward mutations in intact mammalian cells.
authors.affiliation: Department of Genetics, Microbiology and Toxicology (GMT), Arrhenius Laboratories of Natural Sciences, Stockholm University, Stockholm, Sweden.
authors.forename: Anne
authors.initials: A
authors.lastname: Lagerqvist
authors.forename: Daniel
authors.initials: D
authors.lastname: Håkansson
authors.forename: Gabriela
authors.initials: G
authors.lastname: Prochazka
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lundin
authors.forename: Kristian
authors.initials: K
authors.lastname: Dreij
authors.forename: Dan
authors.initials: D
authors.lastname: Segerbäck
authors.forename: Bengt
authors.initials: B
authors.lastname: Jernström
authors.forename: Margareta
authors.initials: M
authors.lastname: Törnqvist
authors.forename: Albrecht
authors.initials: A
authors.lastname: Seidel
authors.forename: Klaus
authors.initials: K
authors.lastname: Erixon
authors.forename: Dag
authors.initials: D
authors.lastname: Jenssen
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000493:pharmacokinetics / Q000633:toxicity*; D000818:Animals; D001580:Benzopyrenes / Q000493:pharmacokinetics / Q000633:toxicity*; D002460:Cell Line; D002855:Chromatography, Thin Layer; D006224:Cricetinae; D003412:Cricetulus; D004260:DNA Repair; D004261:DNA Replication; D004305:Dose-Response Relationship, Drug; D004852:Epoxy Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D006207:Half-Life; D009154:Mutation
chemical_list: D001580:Benzopyrenes; D004852:Epoxy Compounds; C121930:dibenzo(a,l)pyrene diol epoxide; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide