1992 Fiscal Year Final Research Report Summary
ORIGIN OF SPONTANEOUS AND INDUCED MUTATIONS
| Project/Area Number |
03454550
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
放射線5生物学
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
YAMAMOTO Kazuo Tohoku University Faculty of Science Associate Professor, 理学部, 助教授 (20093536)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Spontaneous mutation / Induced mutation / IS element / Deletion mutation / Direct repeat / Base substitution / Hydrogen peroxide / Hydroxy radical |
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| Research Abstract |
We have obtained via DNA sequence analysis a spectrum of spontaneous mutations occurring in the tonB gene on the chromosome and supE gene on the plasmid of E. coli. More than two thirds of all tonB mutations were due to IS elements insertion. In the uvrA defective strain, IS10 was the only element observed and clustered at the specific hotspot site. An analysis of the local DNA sequence indicated that IS10 hotspot in the uvrA was not at all match with the published consensus sequence. It was therefore suggested that the uvrA protein involved for IS10 transposition. In general, IS transposition may be the most important factors for spontaneous mutagenesis. With regard to deletion formation, it was found that recA did not affect tonB-trp deletion formation, and that there existed no direct repeat at the junction of tonB-trp deletion. When pZ189 plasmid was propagated in wild type E. coli, spontaneous mutation frequency of the supE gene was 3.03 -1 x 10 per replication. Among 51 supE mutations analyzed by DNA sequencing, 63% were base substitutions and 25% were IS elements insertions. The base substitutions included both transversions (85%) and transitions (15%), the largest single group being G:C to T:A transversions. Thus, the source of the spontaneous base substitution mutations may be the active oxygen induced G damage formed in DNA during normal metabolism in E. coli.
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