title: Ataxia-telangiectasia mutated kinase regulates ribonucleotide reductase and mitochondrial homeostasis.
abstract: Ataxia-telangiectasia mutated (ATM) kinase orchestrates nuclear DNA damage responses but is proposed to be involved in other important and clinically relevant functions. Here, we provide evidence for what we believe are 2 novel and intertwined roles for ATM: the regulation of ribonucleotide reductase (RR), the rate-limiting enzyme in the de novo synthesis of deoxyribonucleoside triphosphates, and control of mitochondrial homeostasis. Ataxia-telangiectasia (A-T) patient fibroblasts, wild-type fibroblasts treated with the ATM inhibitor KU-55933, and cells in which RR is inhibited pharmacologically or by RNA interference (RNAi) each lead to mitochondrial DNA (mtDNA) depletion under normal growth conditions. Disruption of ATM signaling in primary A-T fibroblasts also leads to global dysregulation of the R1, R2, and p53R2 subunits of RR, abrogation of RR-dependent upregulation of mtDNA in response to ionizing radiation, high mitochondrial transcription factor A (mtTFA)/mtDNA ratios, and increased resistance to inhibitors of mitochondrial respiration and translation. Finally, there are reduced expression of the R1 subunit of RR and tissue-specific alterations of mtDNA copy number in ATM null mouse tissues, the latter being recapitulated in tissues from human A-T patients. Based on these results, we propose that disruption of RR and mitochondrial homeostasis contributes to the complex pathology of A-T and that RR genes are candidate disease loci in mtDNA-depletion syndromes.
authors.affiliation: Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520-8023, USA.
authors.forename: Jana S
authors.initials: JS
authors.lastname: Eaton
authors.forename: Z Ping
authors.initials: ZP
authors.lastname: Lin
authors.forename: Alan C
authors.initials: AC
authors.lastname: Sartorelli
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Bonawitz
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Shadel
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D015971:Gene Expression Regulation, Enzymologic; D006706:Homeostasis; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation