title: Effects of ectopic expression of Drosophila DNA glycosylases dOgg1 and RpS3 in mitochondria.
abstract: The main purpose of this study was to determine whether enhancement of repair capacity would attenuate mitochondrial DNA oxidative damage and result in greater cell survival under stressful conditions. The repair of oxidative damage is initiated by DNA glycosylases, which catalyze the excision of oxidized bases, such as 8-hydroxydeoxyguanosine (8-oxodG). Drosophila DNA glycosylases, dOgg1 and RpS3, were ectopically expressed within the mitochondrial matrix in Drosophila S2 cells, causing a severalfold decrease in the levels of 8-oxodG in mitochondrial DNA. Unexpectedly, cells did not show increased resistance to oxidative stress, but instead became more susceptible to treatment with hydrogen peroxide or paraquat. Even in the absence of oxidative challenge, cells expressing RpS3 or dOgg1 in mitochondria exhibited increased apoptosis relative to controls, as determined by flow-cytometric analysis of Annexin V and DNA degradation measured by the Comet assay. Another notable finding was that ectopic expression of either dOgg1 or RpS3 in mitochondria increased cell survival after exposure to the nitric oxide donor SNAP. These results suggest that ectopic expression of one of the constituents of the DNA repair system in mitochondria may cause a perturbation in the base excision repair pathway and lower, rather than enhance, survivability.
authors.affiliation: Department of Biological Sciences, Southern Methodist University, Dedman Life Sciences Building, Room 338, 6501 Airline, Dallas, TX 75275, USA.
authors.forename: Svetlana N
authors.initials: SN
authors.lastname: Radyuk
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Michalak
authors.forename: Igor
authors.initials: I
authors.lastname: Rebrin
authors.forename: Rajindar S
authors.initials: RS
authors.lastname: Sohal
authors.forename: William C
authors.initials: WC
authors.lastname: Orr
mesh_terms: D000818:Animals; D017209:Apoptosis; D002470:Cell Survival; D020552:Comet Assay; D053938:DNA Fragmentation; D045647:DNA Glycosylases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D004272:DNA, Mitochondrial / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000201:enzymology*; D005786:Gene Expression Regulation; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D012269:Ribosomal Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D004272:DNA, Mitochondrial; D029721:Drosophila Proteins; D012269:Ribosomal Proteins; C115334:ribosomal protein S3a, insect; D006861:Hydrogen Peroxide; D045647:DNA Glycosylases; C516999:Ogg1 protein, Drosophila; D010269:Paraquat