Abstract
Purpose: To determine the change in radiosensitivity of Escherichia coli by overexpression of various DNA glycosylases, which may provide an evidence of in vivo response against radiation-induced clustered DNA damage in Escherichia coli. Materials and methods: Quantitative survival assay was performed in alpha-ray, gamma-ray, X-ray and H2O2 survival experiments. Results and Conclusion: The mutant defective in MutM, Nth, Nei DNA glycosylases (mutMnthnei) was less sensitive to gamma-rays and X-rays than the wild-type strain. Overexpression of MutM and human Ogg1 resulted in enhanced sensitivity to such low LET radiation. The enhancement of radiation sensitivity occurred in a dose-dependent fashion. On the contrary, the mutMnthnei mutant was more sensitive to hydrogen peroxide than the wild-type strain. Clustered DNA damage may be transformed into double strand breaks by DNA glycosylases that excise closely opposing lesions, or lesions closed to opposing strand breaks. The level of the increase in radiosensitivity depends on the substrate specificity of DNA glycosylases. [J Radiat Res 44:408 (2003)]
