Autophosphorylation of ataxia-telangiectasia mutated is regulated by protein phosphatase 2A.

Abstract	Ionizing radiation induces autophosphorylation of the ataxia-telangiectasia mutated (ATM) protein kinase on serine 1981; however, the precise mechanisms that regulate ATM activation are not fully understood. Here, we show that the protein phosphatase inhibitor okadaic acid (OA) induces autophosphorylation of ATM on serine 1981 in unirradiated cells at concentrations that inhibit protein phosphatase 2A-like activity in vitro. OA did not induce gamma-H2AX foci, suggesting that it induces ATM autophosphorylation by inactivation of a protein phosphatase rather than by inducing DNA double-strand breaks. In support of this, we show that ATM interacts with the scaffolding (A) subunit of protein phosphatase 2A (PP2A), that the scaffolding and catalytic (C) subunits of PP2A interact with ATM in undamaged cells and that immunoprecipitates of ATM from undamaged cells contain PP2A-like protein phosphatase activity. Moreover, we show that IR induces phosphorylation-dependent dissociation of PP2A from ATM and loss of the associated protein phosphatase activity. We propose that PP2A plays an important role in the regulation of ATM autophosphorylation and activity in vivo.
Authors	Aaron A Goodarzi, Jyoti C Jonnalagadda, Pauline Douglas, David Young, Ruiqiong Ye, Greg B G Moorhead, Susan P Lees-Miller, Kum Kum Khanna
Journal	The EMBO journal (EMBO J) Vol. 23 Issue 22 Pg. 4451-61 (Nov 10 2004) ISSN: 0261-4189 [Print] England
PMID	15510216 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Alexa 488 hydrazide Cell Cycle Proteins DNA-Binding Proteins Enzyme Inhibitors Fluorescent Dyes Hydrazines Tumor Suppressor Proteins Green Fluorescent Proteins Okadaic Acid Serine ATM protein, human Ataxia Telangiectasia Mutated Proteins Protein Serine-Threonine Kinases Phosphoprotein Phosphatases Protein Phosphatase 2
Topics	Ataxia Telangiectasia Ataxia Telangiectasia Mutated Proteins Catalytic Domain Cell Cycle Proteins (chemistry, metabolism) Cell Line Comet Assay DNA-Binding Proteins (chemistry, metabolism) Enzyme Inhibitors (pharmacology) Fibroblasts (radiation effects) Fluorescent Antibody Technique, Indirect Fluorescent Dyes Gene Deletion Gene Expression Regulation Genes, Dominant Green Fluorescent Proteins (metabolism) Humans Hydrazines Microscopy, Confocal Models, Biological Okadaic Acid (pharmacology) Phosphoprotein Phosphatases (chemistry, drug effects, genetics, metabolism) Phosphorylation Precipitin Tests Protein Phosphatase 2 Protein Serine-Threonine Kinases (chemistry, metabolism) Protein Structure, Tertiary Radiation, Ionizing Serine (chemistry) Signal Transduction Tumor Suppressor Proteins (chemistry, metabolism) Two-Hybrid System Techniques

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