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RPS25 is essential for translation initiation by the Dicistroviridae and hepatitis C viral IRESs

Dori M Landry1, Marla I Hertz, Sunnie R Thompson

  • 1Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.

Genes & Development
|December 3, 2009
PubMed

Insights

Ribosomal protein Rps25 is crucial for internal ribosome entry site (IRES)-mediated translation initiation in yeast and mammalian cells. This finding reveals a specific role for Rps25 in cap-independent translation, distinct from its function in cap-dependent processes.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Most eukaryotic messenger RNAs (mRNAs) use cap-dependent translation.
  • A subset of mRNAs, around 10%, utilize cap-independent translation via internal ribosome entry sites (IRES).
  • The mechanisms governing IRES-mediated translation remain incompletely understood.

Purpose of the Study:

  • To elucidate the role of ribosomal proteins in IRES-mediated translation initiation.
  • To identify specific factors required for the recruitment of ribosomes to IRES elements.
  • To understand the molecular interactions between IRES elements and the translation machinery.

Main Methods:

  • Utilized yeast genetics to investigate IRES function.
  • Performed in vitro assays with purified ribosomal subunits.
  • Examined the role of Rps25 in both IRES-mediated and cap-dependent translation in yeast and mammalian cells.

Main Results:

  • Rps25p was identified as essential for cricket paralysis virus (CrPV) intergenic region IRES activity in yeast and mammalian cells.
  • 40S ribosomal subunits lacking Rps25 demonstrated impaired binding to the IRES in vitro.
  • The requirement for Rps25 was conserved across different IRES types, including the hepatitis C virus (HCV) IRES.
  • Yeast strains deficient in Rps25 showed minimal defects in other translation-related processes.

Conclusions:

  • Rps25 is specifically required for IRES-mediated translation initiation, not for cap-dependent translation.
  • This study provides the first evidence of a ribosomal protein uniquely essential for IRES function.
  • Findings lay the groundwork for a model detailing IRES-ribosome interactions.

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