Identification and Characterization of Novel DNA Glycosylases Involved in Base Excision Repair for Oxidative Base Damage in DNA

Abstract

Reactive oxygen species and ionizing radiation induce a wide variety of oxidative modifications to purines and pyrimidine bases in DNA. Bacteria, yeast and eukaryotes have evolved base excision repair mechanisms for oxidative base damage in DNA. Base excision repair is initiated by DNA glycosylase through the removal of modified bases from the DNA. E. coli has three kinds of DNA glycosylase, MutM, Nth and Nei, that recognize and remove oxidatively damaged bases from DNA. These DNA glycosylases are able to recognize and remove 5-formyluracil and 5-hydroxymethyluracil from DNA. Moreover, several evidence showed that there are residual activities to repair 5-foU-containing duplex DNA in crude extract from E. coli mutM nth nei mutant, suggesting possible roles of another DNA glycosylase(s). We identified and purified the novel protein to recognize and repair the duplex oligonucleotides containing 5-foU. We are currently investigating the structure and functions of the protein. Furthermore, we found some novel proteins in C. elegans that rescue the spontaneous mutations in E. coli mutM nth nei mutant.