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Purification of Ubiquitinated p53 Proteins from Mammalian Cells
10:55

Purification of Ubiquitinated p53 Proteins from Mammalian Cells

Published on: March 21, 2022

Mdm2 facilitates the association of p53 with the proteasome

Roman Kulikov1, Justine Letienne, Manjit Kaur

  • 1Karlsruhe Institute of Technology, Institute of Toxicology and Genetics, P.O. Box 3640, 76021 Karlsruhe, Germany.

Proceedings of the National Academy of Sciences of the United States of America
|May 19, 2010
PubMed

Insights

The Mdm2 protein targets p53 for degradation. Phosphorylation sites in Mdm2 regulate its interaction with the proteasome, controlling p53 degradation post-ubiquitylation.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • The ubiquitin ligase Mdm2 is a key regulator of the p53 tumor suppressor.
  • Mdm2 targets p53 for degradation via the proteasome.
  • Mutations in Mdm2's phosphorylation sites suggest a post-ubiquitylation role in p53 degradation.

Purpose of the Study:

  • To investigate the role of Mdm2 in p53 proteasomal degradation.
  • To elucidate the mechanism by which Mdm2 interacts with the proteasome.
  • To determine how Mdm2 phosphorylation sites affect p53 degradation and proteasome association.

Main Methods:

  • Site-directed mutagenesis of Mdm2 phosphorylation sites.
  • Co-immunoprecipitation assays to study protein interactions.
  • Analysis of Mdm2-p53-proteasome ternary complex formation.

Main Results:

  • Mdm2 binds to proteasome subunits independently of ubiquitylation.
  • Mdm2 promotes the formation of a ternary complex with p53 and the proteasome.
  • Mutating Mdm2 phosphorylation sites impairs ternary complex formation and p53 degradation.
  • Mdm2's C-terminus mediates proteasome interaction, while its central domain can inhibit this interaction.

Conclusions:

  • Mdm2 facilitates p53 association with the proteasome.
  • Phosphorylation of Mdm2's central domain regulates this interaction and subsequent p53 degradation.
  • Mdm2 possesses a post-ubiquitylation function critical for p53 degradation.

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