1991 Fiscal Year Final Research Report Summary
Lethal and Mutagenic Lesions Produced in DNA by Exposure to X-Rays and Activi Oxygen Species
| Project/Area Number |
02680168
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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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 | Kyoto University |
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Principal Investigator |
YONEI Shuji Kyoto University, Faculty of Science Assistant Professor, 理学部, 助教授 (60093340)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Active oxygen spesies / X-rays / Oxidative DNA damage / DNA repair / Adaptive response / Gene expression / Mutagenesis |
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| Research Abstract |
1. Mud phage was used to isolate at least four gene fusions to the lacZ gene(soi : : lacZ, soi for superoxide inducible)that were induced by treatment with superoxide generators such as methyl viologen(paraquat)and menadione. The induction of -galactosidase in these fusion strains with the superoxide radical generating agents required aerobic metabolism. Hyperoxygenation(i. e., bubbling of cultures with oxygen gas)also induced the fusions. On the other hand, hydrogen peroxide did not induce the fusions at concentrations that are known to invoke an adaptive response. Introduction of oxyr, htpr or reca mutations did not affect the induction. Three of the fusion strains exhibited increased sensitivity to methyl viologen but not to hydrogen peroxide. All these fusions were located in the 6- to 36-min region of the Escherichia coli chromosome.
2. It was also found that certain membrane-briding drugs(anesthetics)which disturb the membrane-bound respiratory activity induce Mn-superoxide dismutase only under aerobic conditions. The results suggested that such membrane-binding drugs generate superoxide as a result of disruption of the electron transport system of the membrane by the action of the drugs.
3. The experiments revealed that nth and xthnfo mutants of E. coli showed increased sensitivity to mutagenic effect of X-rays and hydrogen peroxide, indicating that thymine glycols and AP sites produced in DNA were a main premutagenic lesion in bacterial cells. It was also found that 8-hydroxy-guanine was also premutagenic and a cause for GC-TA transversion.
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