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Detection and Visualization of DNA Damage-induced Protein Complexes in Suspension Cell Cultures Using the Proximity Ligation Assay
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Activation of the ATM kinase by ionizing radiation and phosphorylation of p53

C E Canman1, D S Lim, K A Cimprich

  • 1The Johns Hopkins School of Medicine, Oncology Center, Baltimore, MD 21205, USA.

Science (New York, N.Y.)
|September 11, 1998
PubMed

Insights

The ATM gene product phosphorylates the p53 tumor suppressor protein at serine-15, a key step in DNA damage response. This protein kinase activity is enhanced by ionizing radiation, suggesting ATM

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Cancer Research

Background:

  • p53 is a crucial tumor suppressor protein activated by DNA damage.
  • Ataxia telangiectasia is a genetic disorder linked to mutations in the ATM gene.
  • DNA damage response pathways involve complex signaling cascades.

Purpose of the Study:

  • To investigate the role of ATM (ataxia telangiectasia mutated) in the phosphorylation of p53.
  • To determine if ATM possesses intrinsic protein kinase activity towards p53.
  • To elucidate the signaling pathway initiated by ionizing radiation involving ATM and p53.

Main Methods:

  • Immunoprecipitation of ATM protein.
  • In vitro kinase assays using immunoprecipitated ATM.
  • Analysis of p53 phosphorylation at serine-15.
  • Comparison of ATM activity in normal and ataxia telangiectasia cells.

Main Results:

  • Immunoprecipitated ATM demonstrated intrinsic protein kinase activity.
  • ATM phosphorylated p53 on serine-15 in a manganese-dependent manner.
  • Ionizing radiation, but not UV radiation, rapidly enhanced ATM's p53-directed kinase activity.
  • Phosphorylation of p53 on serine-15 was reduced in ataxia telangiectasia cells.

Conclusions:

  • ATM functions as a protein kinase that phosphorylates p53 in vivo.
  • ATM is a critical component of the signal transduction pathway activated by ionizing radiation.
  • The findings provide insight into the molecular mechanisms underlying DNA damage response and cancer predisposition.

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