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Updated: Jun 14, 2025

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

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Ribosomal Protein S4 X-Linked as a Novel Modulator of MDM2 Stability by Suppressing MDM2 Auto-Ubiquitination and SCF

Satsuki Ryu1, Hiroki Nakashima1, Yuka Tanaka2

  • 1Faculty of Pharmaceutical Science at Kagawa Campus, Tokushima Bunri University, 1314-1 Shido, Sanuki 769-2193, Japan.

Biomolecules
|August 29, 2024
PubMed

Insights

Ribosomal protein S4X-linked (RPS4X) stabilizes the oncoprotein mouse double minute 2 (MDM2) by preventing its degradation. This interaction is crucial for understanding MDM2 regulation in cancer.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • Mouse double minute 2 (MDM2) is an oncoprotein overexpressed in tumors, promoting cellular transformation.
  • MDM2 plays a critical role in regulating the tumor suppressor p53.
  • Understanding MDM2 regulation is vital for cancer therapy.

Purpose of the Study:

  • To identify novel regulators of MDM2 stability.
  • To elucidate the mechanism by which MDM2 levels are controlled.
  • To explore the function of ribosomal proteins in cancer biology.

Main Methods:

  • Co-immunoprecipitation to identify binding partners of MDM2.
  • Ubiquitination assays to assess MDM2 degradation.
  • Western blotting to measure protein levels.
  • Analysis of protein-protein interactions.

Main Results:

  • Ribosomal protein S4X-linked (RPS4X) was identified as a novel binding partner of MDM2.
  • RPS4X enhances MDM2 stability by suppressing its polyubiquitination and auto-ubiquitination.
  • RPS4X inhibits the MDM2 interaction with Cullin1, a component of the SCF E3 ubiquitin ligase complex.
  • RPS4X expression increases steady-state MDM2 protein levels.

Conclusions:

  • RPS4X is a novel stabilizer of MDM2, impacting its degradation pathway.
  • This study reveals a new mechanism for MDM2 regulation involving ribosomal proteins.
  • The findings expand the known functions of ribosomal proteins and offer insights into cancer cell mechanisms.
Keywords:
Cullin1MDM2RPS4XSCF complexubiquitination

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