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base excision repair; catalase; DNA glycosylase; NEIL; OGG1; Schizosaccharomyces pombe.
Human cells have five DNA glycosylases OGG1, NTHL1, NEIL1, NEIL2, and NEIL3 with overlapping substrate ranges to repair damage to oxidative bases. To investigate the DNA repair activity of each enzyme in vivo, we expressed OGG1 and three NEIL-family proteins in a fission yeast Schzosaccharomyces pombe lacking catalase and DNA glycosylase Nth1p activities. S. pombe Nth1p is a unique enzyme that excises oxidatively modified bases in the yeast cells, and a defect of the catalase gene (ctt1) enhances the sensitivity of nth1∆ cells to H2O2. Complementation of the yeast H2O2-sensitivity by OGG1 and NEIL-family proteins showed that all enzymes efficiently initiated base excision repair to correct H2O2-damaged DNA in vivo. The nth1∆/ctt1∆ cells were also sensitive to an alkylating agent methyl methanesulfonate (MMS) by accumulating AP sites. Based on the ability to complement MMS sensitivity, human DNA glycosylases were shown to act on AP sites more weakly than S. pombe Nth1p. Moreover, we showed that some NEIL3 mutants could complement the DNA repair activity of nth1∆/ctt1∆ cells in vivo. The results of this study also indicate that S. pombe ctt1∆/nth1∆ cells provide a useful heterologous expression system to investigate the in vivo function of DNA glycosylase.
Research papers (publications of university or research institution)
