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Purification of Ubiquitinated p53 Proteins from Mammalian Cells
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Purification of Ubiquitinated p53 Proteins from Mammalian Cells

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Inhibition of p53 degradation by Mdm2 acetylation

Xinjiang Wang1, Jan Taplick, Naama Geva

  • 1Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel.

FEBS Letters
|March 12, 2004
PubMed

Insights

Mdm2, a protein that degrades p53, is itself acetylated by CBP and p300. This acetylation, particularly in the RING finger domain, impairs Mdm2

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Mdm2 (mouse double minute 2 homolog) is a RING finger E3 ubiquitin ligase.
  • Mdm2 targets the p53 tumor suppressor protein for ubiquitination and proteasomal degradation.
  • Acetylation of p53 influences its transcriptional activity and inhibits Mdm2-mediated degradation.

Purpose of the Study:

  • To investigate whether Mdm2 is also a target of acetylation.
  • To determine the functional consequences of Mdm2 acetylation on p53 regulation.

Main Methods:

  • In vitro acetylation assays using purified proteins and cell extracts.
  • Identification of acetylation sites and domains within Mdm2.
  • In vivo acetylation studies in cells.
  • Analysis of Mdm2 activity using a mutant mimicking acetylation (K466/467Q).

Main Results:

  • Mdm2 is acetylated in vitro by CREB-binding protein (CBP) and p300, primarily in the RING finger domain.
  • In vivo acetylation of Mdm2 is efficiently mediated by CBP and requires an intact RING finger.
  • An Mdm2 mutant mimicking acetylation (K466/467Q) shows impaired p53 ubiquitination, Mdm2 autoubiquitination, and p53 degradation.

Conclusions:

  • Mdm2 is a novel target for acetylation by CBP and p300.
  • Acetylation of Mdm2, particularly within the RING finger domain, inactivates its E3 ligase activity.
  • Acetyltransferases can modulate cellular p53 activity by directly acetylating and inactivating Mdm2, in addition to acetylating p53.

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