Identifying the interactions conferring functional mechanical rigidity on RNase-resistant RNA from Zika virus.

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• Viruses utilize exoribonuclease-resistant RNAs (xrRNAs) to evade host cell RNA degradation.
• xrRNAs possess a unique structure involving a threaded 5'-end and a pseudoknot, contributing to their stability.
• Previous studies demonstrated the mechanical rigidity of Zika virus xrRNA is key to its RNase resistance.

Purpose of the Study:

• To identify the specific tertiary interactions responsible for the mechanical rigidity of Zika virus xrRNA.
• To understand the relationship between mechanical properties and RNase resistance in xrRNAs.
• To explore potential therapeutic targets within xrRNA structures.

Main Methods:

• Single-molecule force spectroscopy (SMFS) was employed to assess mechanical properties.
• Systematic mutation of tertiary contacts within the Zika virus xrRNA.
• Computational simulations were used to map mechanical tension distribution.

Main Results:

• Disruption of tertiary contacts involving the 5'-end abolished mechanical resistance.
• Breaking a single pseudoknot base pair did not significantly affect mechanical resistance; two were required.
• RNase resistance directly correlated with mechanical resistance across all mutants.

Conclusions:

• Tertiary contacts, particularly those anchoring the 5'-end, are critical for Zika virus xrRNA mechanical rigidity.
• Mechanical rigidity, not just fold topology, is essential for xrRNA's protective function against RNases.
• Understanding these interactions provides insights for developing xrRNA-targeted antiviral therapies.