title: Mitochondrial reactive oxygen species are scavenged by Cockayne syndrome B protein in human fibroblasts without nuclear DNA damage.
abstract: Cockayne syndrome (CS) is a human DNA repair-deficient disease that involves transcription coupled repair (TCR), in which three gene products, Cockayne syndrome A (CSA), Cockayne syndrome B (CSB), and ultraviolet stimulated scaffold protein A (UVSSA) cooperate in relieving RNA polymerase II arrest at damaged sites to permit repair of the template strand. Mutation of any of these three genes results in cells with increased sensitivity to UV light and defective TCR. Mutations in CSA or CSB are associated with severe neurological disease but mutations in UVSSA are for the most part only associated with increased photosensitivity. This difference raises questions about the relevance of TCR to neurological disease in CS. We find that CSB-mutated cells, but not UVSSA-deficient cells, have increased levels of intramitochondrial reactive oxygen species (ROS), especially when mitochondrial complex I is inhibited by rotenone. Increased ROS would result in oxidative damage to mitochondrial proteins, lipids, and DNA. CSB appears to behave as an electron scavenger in the mitochondria whose absence leads to increased oxidative stress. Mitochondrial ROS, however, did not cause detectable nuclear DNA damage even when base excision repair was blocked by an inhibitor of polyADP ribose polymerase. Neurodegeneration in Cockayne syndrome may therefore be associated with ROS-induced damage in the mitochondria, independent of nuclear TCR. An implication of our present results is that mitochondrial dysfunction involving ROS has a major impact on CS-B pathology, whereas nuclear TCR may have a minimal role.
authors.affiliation: Department of Dermatology, University of California, San Francisco, CA 94143; JCleaver@cc.ucsf.edu.
authors.forename: James E
authors.initials: JE
authors.lastname: Cleaver
authors.affiliation: Department of Neurology, University of California, San Francisco and Veterans Affairs Medical Center, San Francisco, CA 94121;
authors.forename: Angela M
authors.initials: AM
authors.lastname: Brennan-Minnella
authors.affiliation: Department of Neurology, University of California, San Francisco and Veterans Affairs Medical Center, San Francisco, CA 94121;
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Swanson
authors.affiliation: Department of Experimental Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: Ka-wing
authors.initials: KW
authors.lastname: Fong
authors.affiliation: Department of Experimental Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202;
authors.forename: Kai-ming
authors.initials: KM
authors.lastname: Chou
authors.affiliation: Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202;
authors.forename: Yih-wen
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Department of Dermatology, University of California, San Francisco, CA 94143; Department of Clinical Chemistry and Hematology, Sint Franciscus Gasthuis, 3045PM, Rotterdam, The Netherlands; and.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Revet
authors.affiliation: Center for Melanoma Research and Treatment, California Pacific Medical Center Research Institute, San Francisco, CA 94107.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bezrookove
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000473:pathology* / Q000528:radiation effects; D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism*; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004996:Ethidium / Q000031:analogs & derivatives / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D000075223:Poly-ADP-Ribose Binding Proteins; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012402:Rotenone / Q000633:toxicity; D014466:Ultraviolet Rays
chemical_list: D002352:Carrier Proteins; C468783:H2AX protein, human; D006657:Histones; D000075223:Poly-ADP-Ribose Binding Proteins; D017382:Reactive Oxygen Species; C573137:UVSSA protein, human; D012402:Rotenone; C067883:dihydroethidium; D006861:Hydrogen Peroxide; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes; D004996:Ethidium
keywords: bromate; comet assay; hydrogen peroxide; oxidative DNA damage; γH2Ax