title: Contribution of the Atm protein to maintaining cellular homeostasis evidenced by continuous activation of the AP-1 pathway in Atm-deficient brains.
abstract: Maintenance of genome stability is essential for keeping cellular homeostasis. The DNA damage response is a central component in maintaining genome integrity. Among of the most cytotoxic DNA lesions are double strand breaks (DSBs) caused by ionizing radiation or radiomimetic chemicals. ATM is missing or inactivated in patients with ataxia-telangiectasia. Ataxia-telangiectasia patients display a pleiotropic phenotype and suffer primarily from progressive ataxia caused by degeneration of cerebellar Purkinje and granule neurons. Additional features are immunodeficiency, genomic instability, radiation sensitivity, and cancer predisposition. Disruption of the mouse Atm locus creates a murine model of ataxia-telangiectasia that exhibits most of the clinical features of the human disease but very mild neuronal abnormality. The ATM protein is a multifunctional protein kinase, which serves as a master regulator of cellular responses to DSBs. There is growing evidence that ATM may be involved in addition to the DSB response in other processes that maintain processes in cellular homeostasis. For example, mounting evidence points to increased oxidative stress in the absence of ATM. Here we report that the AP-1 pathway is constantly active in the brains of Atm-deficient mice not treated with DNA damaging agents. A canonical activation (increased phosphorylation of mitogen-activated protein kinase kinase-4, c-Jun N-terminal kinase, and c-Jun) of the AP-1 pathway was found in Atm-deficient cerebra, whereas induction of the AP-1 pathway in Atm-deficient cerebella is likely to mediate elevated expression of c-Fos and c-Jun. Although Atm(+/+) mice are capable of responding to ionizing radiation by activating stress responses such as the AP-1 pathway, Atm-deficient mice display higher basal AP-1 activity but gradually lose their ability to activate AP-1 DNA-binding activity in response to ionizing radiation. Our results further demonstrate that inactivation of the ATM gene results in a state of constant stress.
authors.affiliation: Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978 Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Weizman
authors.forename: Yosef
authors.initials: Y
authors.lastname: Shiloh
authors.forename: Ari
authors.initials: A
authors.lastname: Barzilai
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008099:Liver / Q000378:metabolism; D048768:MAP Kinase Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013687:Telencephalon / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D025521:Tumor Suppressor Proteins; D012694:Serine; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048768:MAP Kinase Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases; C482779:MAP3K4 protein, human; C482780:Map3k4 protein, mouse