title: Saccharomyces cerevisiae Ogg1 prevents poly(GT) tract instability in the mitochondrial genome.
abstract: Reactive oxygen species can attack the mitochondrial genome to produce a vast array of oxidative DNA lesions including 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo). We assess the role of the Saccharomyces cerevisiae 8-oxo-dGuo DNA glycosylase, Ogg1, in the maintenance of a poly(GT) tract reporter system present in the mitochondrial genome. Deletion in the poly(GT) tract causes the reporter system to produce arginine-independent (Arg+) colonies. We show that the mitochondrial form of Ogg1 is functionally active at processing 8-oxo-dGuo lesions and that Ogg1-deficient cells exhibit nearly six-fold elevated rate of Arg+ mutants under normal growth condition, as compared to the parent. Overexpression of Ogg1 completely suppressed the high rate of Arg+ mutations to levels lower than the parental, suggesting that Ogg1 function could be limited in the mitochondria. Further analysis revealed that the Arg+ mutations can be prevented if the cells are grown under anaerobic conditions. These findings provide in vivo evidence that oxidative stress induces the formation of lesions, most likely 8-oxo-dGuo, which must be repaired by Ogg1, otherwise the lesions can trigger poly(GT) tract instability in the mitochondrial genome. We also demonstrate that overproduction of the major apurinic/apyrimidinic (AP) endonuclease Apn1, a nuclear and mitochondrial enzyme with multiple DNA repair activities, substantially elevated the rate of Arg+ mutants, but which was counteracted by Ogg1 overexpression. We suggest that Ogg1 might bind to AP sites and protect this lesion from the spurious action of Apn1 overproduction. Thus, cleavage of AP site located within or in the vicinity of the poly(GT) tract could destabilize this repeat.
authors.affiliation: University of Montreal, Maisonneuve-Rosemont Hospital, Guy-Bernier Research Centre, 5415 de l'Assomption, Montreal, Que., Canada H1T 2M4.
authors.forename: Ratsavarinh
authors.initials: R
authors.lastname: Vongsamphanh
authors.forename: J Richard
authors.initials: JR
authors.lastname: Wagner
authors.forename: Dindial
authors.initials: D
authors.lastname: Ramotar
mesh_terms: D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D045647:DNA Glycosylases / Q000235:genetics* / Q000502:physiology*; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D016681:Genome, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018895:Microsatellite Repeats; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000502:physiology*; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D004272:DNA, Mitochondrial; D005656:Fungal Proteins; D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; C097188:polyglutamine; D001120:Arginine; D045647:DNA Glycosylases; C505160:Ogg1 protein, S cerevisiae