Mutagenesis, Vol. 14, No. 2, 249-253,
March 1999
© 1999 UK Environmental Mutagen Society/Oxford University Press
Cobaltous chloride-induced mutagenesis in the supF tRNA gene of Escherichia coli
1 Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, Tobata-ku, Kitakyushu 804-8550, 2 Department of Biochemical Engineering and Science, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu, Iizuka 820-8502 and 3 Biological Institute, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
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.
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