Journal of Radiation Research
Online ISSN : 1349-9157
Print ISSN : 0449-3060
Regular Papers
The Shizosaccharomyces pombe Homolog (SpMYH) of the Escherichia coli MutY Is Required for Removal of Guanine from 8-Oxoguanine/Guanine Mispairs to Prevent G:C to C:G Transversions
Takashi DOIShin-Ichiro YONEKURAKeizo TANOShinji YASUHIRAShuji YONEIQiu-Mei ZHANG
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2005 Volume 46 Issue 2 Pages 205-214

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Abstract

The frequency of G:C→C:G transversions significantly increases upon exposure of cells to ionizing radiation or reactive oxygen species. Transversions can be prevented by base excision repair, which removes the causative modified bases from DNA. Our previous studies revealed that MutY is responsible for removing guanine from 7,8-dihydro-8-oxoguanine/guanine mispairs (8-oxoG/G) and prevents the generation of G:C→C:G transversions in E. coli. SpMYH, a homolog of E. coli MutY, had been identified and characterized in the fission yeast S. pombe. Purified SpMYH has adenine DNA glycosylase activity on A/8-oxoG and A/G mismatch-containing oligonucleotides. In this study, we examined whether SpMYH has a similar activity allowing it to remove G from 8-oxoG/G in DNA. The purified SpMYH tightly bound to duplex oligonucleotides containing 8-oxoG/G and removed the unmodified G from 8-oxoG/G as efficiently as A from 8-oxoG/A. The activity was absent in the cell extract prepared from an SpMYH-knockout strain of S. pombe. The expression of SpMYH markedly reduced the frequency of spontaneous G:C→C:G transversions in the E. coli mutY mutant. These results demonstrate that SpMYH is involved in the repair of 8-oxoG/G, by which it prevents mutations induced by oxidative stress in S. pombe.

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© 2005 by Journal of Radiation Research Editorial Committee
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