Abstract
8-oxoguanine (8-oxoG) is an abundant and critical base modification. It is excised from the DNA by MutM in E. coli and Ogg1 in S. cerevisiae and mammalian cells. However, any structural and functional homologs of them are not yet identified in Shizosaccharomyces pombe. Recently, Nth-Spo, an ortholog of E. coli Nth, was cloned from the S. pombe. It removes oxidative pyrimidines from the DNA. E. coli Nth and Nei remove 8-oxoG from the 8-oxoG:G mispairs in DNA. We examined whether the Nth-Spo functions as a DNA glycosylase/AP lyase for 8-oxoG in DNA. The Nth-Spo was expressed in E. coli and partially purified using glutathione affinity column chromatography. The DNA glycosylase activity was assayed for 8-oxoG:A, 8-oxoG:G or 8-oxoG:C containing duplex oligonucleotides. The Nth-Spo efficiently removed 8-oxoG from 8-oxoG:A and 8-oxoG:G pairs from DNA. The activity to remove 8-oxoG from 8-oxoG:A and 8-oxoG:G mispairs was much higher than that from 8-oxoG:C. Furthermore, we report about the effects of Nth-Spo expression in mutMmutY and nthnei mutants of E. coli. [J Radiat Res 44:412 (2003)]
