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Cooperation between the ribosomal proteins L5 and L11 in the p53 pathway

H F Horn1, K H Vousden

  • 11The Beatson Institute for Cancer Research, Bearsden, Glasgow, UK.

Oncogene
|June 19, 2008
PubMed

Insights

Ribosomal proteins L5 and L11 cooperate to inhibit MDM2, stabilizing the p53 tumor suppressor. This interaction, dependent on L11 binding 5S rRNA, enhances p53 activation.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • MDM2 is a ubiquitin ligase crucial for p53 tumor suppressor protein stability.
  • Inhibition of MDM2's E3 ligase activity leads to p53 accumulation and pathway activation.
  • Proteins like ARF, L5, and L11 are known to inhibit MDM2.

Purpose of the Study:

  • To investigate the cooperative inhibition of MDM2 by ribosomal proteins L5 and L11.
  • To determine the role of 5S rRNA binding in L11's interaction with MDM2 and L5.
  • To compare the inhibitory potency of L11 and p14(ARF) on MDM2.

Main Methods:

  • Overexpression of L5 and L11 proteins in cellular systems.
  • Assays to measure MDM2 E3 ligase activity.
  • Western blotting to assess p53 protein levels and activation.
  • Analysis of L11's 5S rRNA binding capability using mutant constructs.

Main Results:

  • L11 alone is less potent in inhibiting MDM2 than p14(ARF).
  • Coexpression of L5 and L11 results in robust inhibition of MDM2 E3 activity.
  • This cooperation leads to significant p53 stabilization and activation, comparable to p14(ARF).
  • L11's ability to bind 5S rRNA is essential for its cooperation with L5.

Conclusions:

  • Ribosomal proteins L5 and L11 synergistically inhibit MDM2 activity.
  • The L5-L11 complex effectively stabilizes and activates the p53 tumor suppressor.
  • 5S rRNA binding is a critical factor for L11's cooperative function with L5 in regulating MDM2.

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