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DNA damage-induced phosphorylation of p53 alleviates inhibition by MDM2

S Y Shieh1, M Ikeda, Y Taya

  • 1Department of Biological Sciences, Columbia University, New York, New York 10027, USA.

Cell
|November 18, 1997
PubMed

Insights

DNA damage triggers p53 activation via phosphorylation at serine 15, reducing its interaction with MDM2. This phosphorylation, particularly by DNA-dependent protein kinase (DNA-PK), enhances p53

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Cancer Research

Background:

  • DNA-damaging agents activate the tumor suppressor p53 through posttranscriptional mechanisms.
  • The interaction between p53 and its negative regulator, MDM2 (murine double minute 2), is critical for p53 regulation.
  • The precise molecular events linking DNA damage to p53 activation remain incompletely understood.

Purpose of the Study:

  • To elucidate the posttranscriptional mechanisms by which DNA damage signals to p53.
  • To investigate the role of p53 phosphorylation in modulating its interaction with MDM2.
  • To determine the functional consequences of p53 phosphorylation on p53-dependent transactivation.

Main Methods:

  • Western blotting to detect p53 phosphorylation at serine 15.
  • Co-immunoprecipitation assays to assess p53-MDM2 interactions in vitro and in vivo.
  • In vitro kinase assays using purified DNA-dependent protein kinase (DNA-PK) and p53.
  • Reporter assays to measure p53-dependent transactivation activity.

Main Results:

  • Phosphorylation of human p53 at serine 15 occurs following DNA damage.
  • Phosphorylation at serine 15 reduces the in vivo and in vitro interaction between p53 and MDM2.
  • Phosphorylation of p53 at serines 15 and 37 by DNA-PK impairs MDM2's ability to inhibit p53 transactivation.
  • These effects are attributed to a phosphorylation-induced conformational change in p53.

Conclusions:

  • Phosphorylation of p53 at serine 15 is a key posttranscriptional event linking DNA damage to p53 activation.
  • This phosphorylation event disrupts the p53-MDM2 interaction, relieving MDM2-mediated repression of p53.
  • DNA-PK and potentially other kinases mediate p53 phosphorylation, providing a mechanism for p53 induction in response to DNA damage.

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