title: Increased oxidative stress in AOA3 cells disturbs ATM-dependent DNA damage responses.
abstract: Ataxia telangiectasia (AT) is caused by a mutation in the ataxia-telangiectasia-mutated (ATM) gene; the condition is associated with hyper-radiosensitivity, abnormal cell-cycle checkpoints, and genomic instability. AT patients also show cerebellar ataxia, possibly due to reactive oxygen species (ROS) sensitivity in neural cells. The ATM protein is a key regulator of the DNA damage response. Recently, several AT-like disorders have been reported. The genes responsible for them are predicted to encode proteins that interact with ATM in the DNA-damage response. Ataxia with oculomotor apraxia types 1-3 (AOA1, 2, and 3) result in a neurodegenerative and cellular phenotype similar to AT; however, the basis of this phenotypic similarity is unclear. Here, we show that the cells of AOA3 patients display aberrant ATM-dependent phosphorylation and apoptosis following γ-irradiation. The ATM-dependent response to H2O2 treatment was abrogated in AOA3 cells. Furthermore, AOA3 cells had reduced ATM activity. Our results suggest that the attenuated ATM-related response is caused by an increase in endogenous ROS in AOA3 cells. Pretreatment of cells with pyocyanin, which induces endogenous ROS production, abolished the ATM-dependent response. Moreover, AOA3 cells had decreased homologous recombination (HR) activity, and pyocyanin pretreatment reduced HR activity in HeLa cells. These results indicate that excess endogenous ROS represses the ATM-dependent cellular response and HR repair in AOA3 cells. Since the ATM-dependent cell-cycle checkpoint is an important block to carcinogenesis, such inactivation of ATM may lead to tumorigenesis as well as neurodegeneration.
authors: Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan. Electronic address: jkobayashi@house.rbc.kyoto-u.ac.jp.
authors: Junya
authors: J
authors: Kobayashi
authors: Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan.
authors: Yuichiro
authors: Y
authors: Saito
authors: Biomedical Engineering Center, Toin University of Yokohama, Yokohama 225-8503, Japan.
authors: Michiyo
authors: M
authors: Okui
authors: Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan.
authors: Noriko
authors: N
authors: Miwa
authors: Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Kyoto 606-8501, Japan.
authors: Kenshi
authors: K
authors: Komatsu
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism*; D015153:Blotting, Western; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair; D005720:Gamma Rays; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects*; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D011710:Pyocyanine / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D059767:Recombinational DNA Repair / Q000187:drug effects / Q000528:radiation effects*; D020754:Spinocerebellar Ataxias / Q000151:congenital; D013132:Spinocerebellar Degenerations / Q000235:genetics / Q000378:metabolism / Q000473:pathology
chemical_list: D018797:Cell Cycle Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; D016877:Oxidants; D017382:Reactive Oxygen Species; D011710:Pyocyanine; D006861:Hydrogen Peroxide; D064007:Ataxia Telangiectasia Mutated Proteins
keywords: AOA3; ATM; Cell cycle checkpoint; Homologous recombination; Oxidative stress