Structure of RNA Stem Loop B from the Picornavirus Replication Platform.

Area of Science:

• Structural Biology
• Virology
• Molecular Biology

Background:

• Picornavirus RNA replication relies on a cloverleaf structure in the 5'-untranslated region.
• Stem Loop B (SLB) within the cloverleaf is vital for switching between translation and replication.
• SLB serves as a binding site for the host polyC-binding protein, initiating this switch.

Purpose of the Study:

• To elucidate the solution structure of human rhinovirus isotype 14 Stem Loop B (SLB).
• To understand the structural basis for polyC-binding protein recognition and replication initiation.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to determine the 3D structure.
• Analysis of helical parameters, base pairing, and flexibility within the SLB structure.

Main Results:

• SLB adopts a predominantly A-form helical structure with a five Watson-Crick and one wobble base pair stem.
• The eight-nucleotide loop exhibits flexibility, particularly the pyrimidine-rich region, which is the polyC-binding protein recognition site.
• The wobble base pair perturbs helical parameters but does not induce significant flexibility; the major groove remains accessible.

Conclusions:

• The determined structure provides insights into the molecular interactions governing picornavirus replication.
• The flexible, disordered loop region is likely key for host polyC-binding protein interaction and the translation-replication switch.
• Structural features suggest accessibility for protein binding and potential modulation of viral processes.