Cloning of a yeast 8-oxoguanine DNA glycosylase reveals the existence of a base-excision DNA-repair protein superfamily

Curr Biol. 1996 Aug 1;6(8):968-80. doi: 10.1016/s0960-9822(02)00641-3.


Background: Reactive oxygen species, ionizing radiation, and other free radical generators initiate the conversion of guanine (G) residues in DNA to 8-oxoguanine (OG), which is highly mutagenic as it preferentially mispairs with adenine (A) during replication. Bacteria counter this threat with a multicomponent system that excises the lesion, corrects OG:A mispairs and cleanses the nucleotide precursor pool of dOGTP. Although biochemical evidence has suggested the existence of base-excision DNA repair proteins specific for OG in eukaryotes, little is known about these proteins.

Results: Using substrate-mimetic affinity chromatography followed by a mechanism-based covalent trapping procedure, we have isolated a base-excision DNA repair protein from Saccharomyces cerevisiae that processes OG opposite cytosine (OG:C) but acts only weakly on OG:A. A search of the yeast genome database using peptide sequences from the protein identified a gene, OGG1, encoding a predicted 43 kDa (376 amino acid) protein, identical to one identified independently by complementation cloning. Ogg1 has OG:C-specific base-excision DNA repair activity and also intrinsic beta-lyase activity, which proceeds through a Schiff base intermediate. Targeted disruption of the OGG1 gene in yeast revealed a second OG glycosylase/lyase protein, tentatively named Ogg2, which differs from Ogg1 in that it preferentially acts on OG:G.

Conclusions: S. cerevisiae has two OG-specific glycosylase/lyases, which differ significantly in their preference for the base opposite the lesion. We suggest that one of these, Ogg1, is closely related in overall three-dimensional structure to Escherichia coli endonuclease III (endo III), a glycosylase/lyase that acts on fragmented and oxidatively damaged pyrimidines. We have recently shown that AlkA, a monofunctional DNA glycosylase that acts on alkylated bases, is structurally homologous to endo III. We have now identified a shared active site motif amongst these three proteins. Using this motif as a protein database searching tool, we find that it is present in a number of other base-excision DNA repair proteins that process diverse lesions. Thus, we propose the existence of a DNA glycosylase superfamily, members of which possess a common fold yet act upon remarkably diverse lesions, ranging from UV photoadducts to mismatches to alkylated or oxidized bases.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • DNA Repair / genetics*
  • DNA-Formamidopyrimidine Glycosylase
  • Escherichia coli Proteins*
  • Molecular Sequence Data
  • Multigene Family
  • N-Glycosyl Hydrolases / genetics*
  • N-Glycosyl Hydrolases / isolation & purification
  • N-Glycosyl Hydrolases / metabolism
  • Oligodeoxyribonucleotides
  • Saccharomyces cerevisiae / genetics*
  • Substrate Specificity


  • Escherichia coli Proteins
  • Oligodeoxyribonucleotides
  • N-Glycosyl Hydrolases
  • DNA-Formamidopyrimidine Glycosylase
  • DNA-formamidopyrimidine glycosylase, E coli