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Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
10:27

Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta

Published on: December 5, 2019

Structural and functional comparison of the RING domains of two p53 E3 ligases, Mdm2 and Pirh2

Jonathan Shloush1, John E Vlassov, Ian Engson

  • 1Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.

The Journal of Biological Chemistry
|November 19, 2010
PubMed

Insights

The E3 ligases Mdm2 and Pirh2 regulate the tumor suppressor p53. Structural analysis reveals distinct mechanisms for Pirh2 and Mdm2 RING domains in p53 ubiquitylation and degradation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • The tumor suppressor p53 is crucial for maintaining genome stability and preventing cancer.
  • Mdm2 and Pirh2 are E3 ligases that target p53 for degradation via ubiquitylation.
  • Understanding the structural and functional differences of these E3 ligases is key to comprehending p53 regulation.

Purpose of the Study:

  • To structurally and functionally compare the RING domains of Pirh2 and Mdm2.
  • To elucidate the distinct mechanisms by which Pirh2 and Mdm2 regulate p53 ubiquitylation and degradation.
  • To provide mechanistic insights into p53 regulation by its E3 ligases.

Main Methods:

  • Structural analysis of Pirh2 and Mdm2 RING domains.
  • Functional assays to assess E3 ligase activity.
  • Nuclear Magnetic Resonance (NMR) spectroscopy.
  • Site-directed mutagenesis studies.

Main Results:

  • The Pirh2 RING domain exhibits unique oligomeric state, surface charge, and zinc coordination compared to Mdm2.
  • Pirh2 displays weaker E3 ligase activity towards p53 and ubiquitinates different p53 residues than Mdm2.
  • While sharing an E2 binding site, Mdm2's C-terminal residues are essential for its E3 ligase activity, a feature absent in Pirh2.

Conclusions:

  • Pirh2 and Mdm2 possess distinct structural and functional properties in their RING domains.
  • These differences dictate differential ubiquitylation and degradation of p53.
  • The study provides critical structural and mechanistic insights into the regulation of p53 by its E3 ligases, Mdm2 and Pirh2.

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