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HDM2 antagonist Nutlin-3 disrupts p73-HDM2 binding and enhances p73 function

L M S Lau1, J K Nugent, X Zhao

  • 1Division of Hematology/Oncology, Department of Paediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada.

Oncogene
|August 19, 2007
PubMed

Insights

Nutlin-3 triggers cell death independently of p53 by targeting p73. This small molecule inhibitor disrupts the p73-HDM2 interaction, enhancing p73

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Death Mechanisms

Background:

  • Nutlin-3 is a small molecule inhibitor known to activate p53 by disrupting its association with HDM2.
  • p53-null cancer cells exhibit Nutlin-3-induced cell death, suggesting a p53-independent mechanism.
  • p73, a homolog of p53, also induces apoptosis and is negatively regulated by HDM2.

Purpose of the Study:

  • To investigate whether p73 mediates Nutlin-3-induced apoptosis in p53-null cells.
  • To elucidate the mechanism of Nutlin-3 action in the context of p53 inactivation.

Main Methods:

  • Assessed the interaction between p73 and HDM2 in p53-null cells treated with Nutlin-3.
  • Measured the transcriptional activity of p73 and the expression of its target genes (noxa, puma, p21).
  • Utilized siRNA to knock down p73 and evaluated the effect on Nutlin-3-induced apoptosis.
  • Determined the impact of Nutlin-3 on TAp73alpha protein levels and half-life.

Main Results:

  • Nutlin-3 inhibited the binding of the proapoptotic p73 isoform TAp73alpha to HDM2 in p53-null cells.
  • This dissociation led to increased p73 transcriptional activity, upregulating target genes noxa, puma, and p21.
  • Nutlin-3 treatment enhanced apoptosis, which was partially rescued by p73 knockdown.
  • Nutlin-3 increased TAp73alpha protein levels and prolonged its half-life.

Conclusions:

  • Nutlin-3 disrupts the endogenous p73-HDM2 interaction, enhancing p73 stability and proapoptotic activity.
  • This p73-dependent mechanism provides a rationale for using Nutlin-3 in human tumors with p53 inactivation.

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