title: Cobaltous chloride-induced mutagenesis in the supF tRNA gene of Escherichia coli.
abstract: The spectrum of mutations induced by cobalt(II) chloride (CoCl2) was examined using plasmid pUB3 DNA, which was propagated after transfection into Escherichia coli SY1032/pKY241 host cells. The vector plasmid carried an E.coli supF suppressor tRNA gene as a target for mutations. After CoCl2 treatment, 64 independent nalidixic acid-resistant, ampicillin-resistant and Lac+ (SupF-) clones were obtained and the altered sequences of the mutated supF genes were determined. Deletions and frameshifts were the predominant mutational event (61%) induced by CoCl2 and base substitutions were induced to a lesser degree (29%). Analysis of sequence alterations at all the sites of mutation revealed that: (i) 18 of 19 base substitutions and eight of 10 frameshifts occurred at G:C sites, suggesting that the formation of N7G-Co(II) adducts may be responsible for premutagenic lesions of these mutations; (ii) short sequence repeats were mostly found at the sites of deletions and frameshifts. Slippage-misalignment is also suggested to be a mechanism for the induction of mutations at these sites.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu, Japan. ogawahi@che.kyutech.ac.jp
authors.forename: H I
authors.initials: HI
authors.lastname: Ogawa
authors.forename: Y
authors.initials: Y
authors.lastname: Ohyama
authors.forename: Y
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: K
authors.initials: K
authors.lastname: Kakimoto
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Shirai
authors.forename: T
authors.initials: T
authors.lastname: Nunoshiba
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D016587:Antimutagenic Agents / Q000633:toxicity*; D003035:Cobalt / Q000633:toxicity*; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics*; D016368:Frameshift Mutation; D017353:Gene Deletion; D016153:Genes, Suppressor; D008957:Models, Genetic; D016296:Mutagenesis; D017354:Point Mutation; D012343:RNA, Transfer / Q000187:drug effects*; D017422:Sequence Analysis, DNA
chemical_list: D016587:Antimutagenic Agents; D004251:DNA Transposable Elements; C096275:supF tRNA; D003035:Cobalt; D012343:RNA, Transfer; C018021:cobaltous chloride