Encephalomyocarditis virus internal ribosomal entry site RNA-protein interactions

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Translational initiation of encephalomyocarditis virus (EMCV) mRNA involves ribosomal entry into the 5' nontranslated region, mediated by internal ribosomal entry sites (IRES).
• IRES elements are crucial for picornavirus and some cellular mRNA translation, requiring trans-acting factors for mRNA-ribosome complex interaction.

Purpose of the Study:

• To identify cellular proteins that interact with the EMCV IRES.
• To elucidate the binding sites of these proteins on the IRES.
• To understand the role of these proteins in IRES-mediated translation.

Main Methods:

• Cross-linking assays using EMCV IRES fragments with cellular extracts (HeLa, rabbit reticulocyte lysate).
• Identification of cross-linked proteins.
• Correlation of protein binding with translation activity.

Main Results:

• Five cellular proteins (p52, p57, p70, p72, and p100) were found to cross-link to the EMCV IRES.
• Binding of p57 to the IRES correlated with translational activity.
• p57 was identified as highly similar to polypyrimidine tract-binding protein.
• Consensus binding sites for p52, p57, p70, and p100 on the IRES were proposed based on binding to 21 different IRES fragments.

Conclusions:

• The identified cellular proteins are likely involved in mediating internal ribosome binding to the EMCV IRES.
• Polypyrimidine tract-binding protein (p57) plays a significant role in EMCV IRES-driven translation.
• These proteins appear to recognize structural features of the IRES RNA rather than specific sequences.