title: Translesion DNA synthesis across various DNA adducts produced by 3-nitrobenzanthrone in Escherichia coli.
abstract: To analyze translesion DNA synthesis (TLS) across lesions derived from the air pollutant 3-nitrobenzanthrone in Escherichia coli, we constructed site-specifically modified plasmids containing single molecule adducts derived from 3-nitrobenzanthrone. For this experiment, we adopted a modified version of the method developed by Fuchs et al. [29]. Each plasmid contained one of the following lesions in its LacZ' gene: N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-N-ABA); 2-(2'-deoxyguanosin-N(2)-yl)-3-aminobenzanthrone (dG-N(2)-C2-ABA); 2-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-C2-ABA); 2-(2'-deoxyadenosin-N(6)-yl)-3-aminobenzanthrone (dA-N(6)-C2-ABA); N-(2'-deoxyguanosin-8-yl)-3-acetylaminobenzanthrone (dG-C8-N-AcABA); or 2-(2'-deoxyguanosin-8-yl)-3-acetylaminobenzanthrone (dG-C8-C2-AcABA). All of the adducts inhibited DNA synthesis by replicative DNA polymerases in E. coli; however, the extent of the inhibition varied among the adducts. All five dG-adducts strongly blocked replication by replicative DNA polymerases; however, the dA-adduct only weakly blocked DNA replication. The induction of the SOS response increased the frequency of TLS, which was higher for the dG-C8-C2-ABA, dG-C8-N-AcABA and dG-C8-C2-AcABA adducts than for the other adducts. In our previous study, dG-C8-N-ABA blocked DNA replication more strongly and induced mutations more frequently than dG-N(2)-C2-ABA in human cells. In contrast, in E. coli the frequency of TLS over dG-N(2)-C2-ABA was markedly reduced, even under the SOS(+) conditions, and dG-N(2)-C2-ABA induced G to T mutations. All of the other adducts were bypassed in a less mutagenic manner. In addition, using E. coli strains that lacked particular DNA polymerases we found that DNA polymerase V was responsible for TLS over dG-C8-N-AcABA and dG-C8-C2-AcABA adducts.
authors.affiliation: Graduate School of Science and Radiation Research Center, Osaka Prefecture University, 1-2 Gakuen-cho, Sakai, Osaka 599-8570, Japan.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kawanishi
authors.forename: Takaharu
authors.initials: T
authors.lastname: Kanno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishida
authors.forename: Tekeji
authors.initials: T
authors.lastname: Takamura-Enya
authors.forename: Takashi
authors.initials: T
authors.lastname: Yagi
mesh_terms: D001551:Benz(a)Anthracenes / Q000633:toxicity*; D018736:DNA Adducts; D004249:DNA Damage; D004261:DNA Replication; D004926:Escherichia coli / Q000187:drug effects*
chemical_list: D001551:Benz(a)Anthracenes; D018736:DNA Adducts; C117220:3-nitrobenzanthrone