Comparison of eubacterial and eukaryotic 5S RNA structures: a chemical modification study

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• 5S ribosomal RNA (rRNA) is a crucial component of ribosomes in all known life forms.
• Understanding the higher-order structure of 5S rRNA is essential for elucidating ribosome assembly and function.
• Comparative structural analysis can reveal evolutionary adaptations and conserved features.

Purpose of the Study:

• To compare and contrast the higher-order structures of 5S rRNAs from a eubacterium (Bacillus stearothermophilus) and a eukaryote (Saccharomyces cerevisiae).
• To investigate the influence of magnesium ions on 5S rRNA structure and stability.
• To map regions of structural divergence and convergence between bacterial and eukaryotic 5S rRNAs.

Main Methods:

• Nucleotide-specific chemical probing of 5S RNAs from Bacillus stearothermophilus and Saccharomyces cerevisiae.
• Monitoring RNA unfolding via thermal denaturation in the presence and absence of magnesium ions.
• Integration of probing data with existing knowledge from ribonuclease digestion studies.

Main Results:

• Evidence for conserved double-helical segments in the secondary structures of both bacterial and eukaryotic 5S rRNAs.
• Identification of specific regions influencing overall RNA folding and tertiary interactions.
• Significant structural differences localized to the loop D/helix IV/loop E/helix V region, with strong evidence for tertiary interactions in eukaryotic loop D.

Conclusions:

• The study provides a detailed picture of the structure and topography of bacterial and eukaryotic 5S rRNAs.
• Key structural distinctions between eubacterial and eukaryotic 5S RNAs are primarily located in the loop D/helix IV/loop E/helix V arm.
• Eukaryotic 5S rRNA loop D is implicated in a critical tertiary interaction, differentiating it from its bacterial counterpart.