In Drosophila, the S3 ribosomal protein has been shown to act as a DNA glycosylase/AP lyase capable of releasing 8-hydroxyguanine (8-OH-Gua) in damaged DNA. Here we describe a second Drosophila protein (dOggl) with 8-OH-Gua and abasic (AP) site DNA repair activities. The Drosophila OGG1 gene codes for a protein of 327 amino acids, which shows 33 and 37% identity with the yeast and human Ogg1 proteins, respectively. The DNA glycosylase activity of purified dOgg1 was investigated using γ-irradiated DNA and gas chromatography/isotope dilution mass spectrometry (GC/IDMS). The dOgg1 protein excises 8-OH-Gua and 2.6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua) from γ-irradiated DNA. with kcat/KM values of 21.0 x 10-5 and 11.2 x 10-5 (min-1 nM-1), respectively. Enzymatic assays using oligodeoxyribonucleotides containing a single lesion show that dOgg1 displays a marked preference for DNA duplexes containing 8-OH-Gua, 8-OH-Ade or AP site placed opposite a cytosine. The cleavage of the 8-OH-Gua-containing strand results from the excision of the damaged DNA base followed by a Β-elimination reaction at the 3'-side of the resulting AP site. Cleavage of 8-OH-Gua.C duplex involves the formation of a reaction intermediate that is converted into a stable covalent adduct in the presence of sodium borohydre dOgg1 complements the mutator phenotype of fpg mutY mutant of Escherichia coli. Whole-mount in situ hybridizations on tissues at different stages of Drosophila development reveal that the dOGG1 messenger is expressed uniformly at a low level in cells in which mitotic division occurs. Therefore, Drosophila possesses two DNA glycosylase activities that can excise 8-OH-Gua and formamidopyrimidines from DNA, dOgg1 and the ribosomal Protein S3.
Citation: Nucleic Acids Research
Issue: No. 23
Pub Type: Journals
8-hydroxyguanine, base-excision repair, drosophila melanogaster, formamidopyrimidine, gas chromatography/mass spectrometry, oxidative DNA damage