title: Ethylene oxide and propylene oxide derived N7-alkylguanine adducts are bypassed accurately in vivo.
abstract: Adducts formed at the nucleophilic N7 position of guanine are the most abundant lesions produced by alkylating agents such as ethylene oxide (EO) and propylene oxide (PO). In order to investigate the intrinsic mutagenic potential of N7-alkylguanine adducts, we prepared single-stranded DNA probes containing a single well-defined N7-alkylguanine adduct under conditions that minimize the presence of depurinated molecules. Following introduction of these probes into Escherichia coli cells, the effect of the N7-alkylguanine adducts on the efficiency and fidelity of replication was determined. To investigate the effect on replication we monitored the relative transformation efficiency of the lesion containing constructs with respect to the control construct. The methyl adduct was found not to be toxic, while the N7-(2-hydroxyethyl)guanine (N7-heG) and N7-(2-hydroxypropyl)guanine (N7-hpG) adducts reduce the transformation efficiency to ≈70% and 40%, respectively. Within the detection limits of our assay, replication across the N7-alkylguanine adducts in vivo is essentially error-free, as no mutant colony was observed among ≈300 individual sequenced colonies (i.e., mutation frequency<0.3%).
authors.affiliation: Cancer Research Center of Marseille, CNRS, UMR7258 Genome Instability and Carcinogenesis (equipe labellisée Ligue Contre le Cancer) Inserm, U1068, Paoli-Calmettes Institute, Aix-Marseille Univ, F-13009 Marseille, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Philippin
authors.affiliation: Lésions des Acides Nucléiques, INAC/SCIB - UMR-E3 CEA/UJF, CEA Grenoble 17 avenue des Martyrs, F-38054 Grenoble Cedex 9, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Cadet
authors.affiliation: Lésions des Acides Nucléiques, INAC/SCIB - UMR-E3 CEA/UJF, CEA Grenoble 17 avenue des Martyrs, F-38054 Grenoble Cedex 9, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Gasparutto
authors.affiliation: Cancer Research Center of Marseille, CNRS, UMR7258 Genome Instability and Carcinogenesis (equipe labellisée Ligue Contre le Cancer) Inserm, U1068, Paoli-Calmettes Institute, Aix-Marseille Univ, F-13009 Marseille, France.
authors.forename: Gerard
authors.initials: G
authors.lastname: Mazon
authors.affiliation: Cancer Research Center of Marseille, CNRS, UMR7258 Genome Instability and Carcinogenesis (equipe labellisée Ligue Contre le Cancer) Inserm, U1068, Paoli-Calmettes Institute, Aix-Marseille Univ, F-13009 Marseille, France. Electronic address: robert.fuchs@inserm.fr.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Fuchs
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity; D018736:DNA Adducts; D004260:DNA Repair; D004261:DNA Replication; D004852:Epoxy Compounds / Q000633:toxicity; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005027:Ethylene Oxide / Q000633:toxicity; D006147:Guanine / Q000031:analogs & derivatives
chemical_list: D000477:Alkylating Agents; D018736:DNA Adducts; D004852:Epoxy Compounds; D006147:Guanine; D005027:Ethylene Oxide; C009068:propylene oxide
keywords: Alkylating agents; N7-alkylguanine adducts; Translesion synthesis