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Activation of the ATM Kinase by Ionizing Radiation and Phosphorylation of p53

Science  11 Sep 1998:
Vol. 281, Issue 5383, pp. 1677-1679
DOI: 10.1126/science.281.5383.1677

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Abstract

The p53 tumor suppressor protein is activated and phosphorylated on serine-15 in response to various DNA damaging agents. The gene product mutated in ataxia telangiectasia, ATM, acts upstream of p53 in a signal transduction pathway initiated by ionizing radiation. Immunoprecipitated ATM had intrinsic protein kinase activity and phosphorylated p53 on serine-15 in a manganese-dependent manner. Ionizing radiation, but not ultraviolet radiation, rapidly enhanced this p53-directed kinase activity of endogenous ATM. These observations, along with the fact that phosphorylation of p53 on serine-15 in response to ionizing radiation is reduced in ataxia telangiectasia cells, suggest that ATM is a protein kinase that phosphorylates p53 in vivo.

  • * Present address: Department of Hematology-Oncology, St. Jude Children's Research Hospital, 332 North Lauderdale Street, D-1034, Memphis, TN 38105–2794, USA.

  • To whom correspondence should be addressed. E-mail: Michael.Kastan{at}stjude.org

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