Multiple Cis-acting elements modulate programmed -1 ribosomal frameshifting in Pea enation mosaic virus

Area of Science:

• Molecular Biology
• Virology
• RNA Structure and Function

Background:

• Programmed -1 ribosomal frameshifting (-1 PRF) is a key mechanism for viral protein synthesis.
• The precise regulation of -1 PRF by downstream cis-elements remains poorly understood.
• Pea enation mosaic virus (PEMV) utilizes -1 PRF for RNA polymerase expression.

Purpose of the Study:

• To elucidate the role of downstream RNA structures in regulating -1 PRF in Umbraviruses.
• To investigate the contribution of the Recoding Stimulatory Element (RSE) and its substructures to frameshifting efficiency.
• To understand how RNA secondary and tertiary structures influence frameshifting levels.

Main Methods:

• Comparative sequence analysis to identify conserved RNA structures.
• Site-directed mutagenesis to alter RSE and lower stem (LS) sequences.
• SHAPE probing to assess RNA structure and conformational changes.
• Ribosomal frameshifting assays to quantify -1 PRF efficiency.

Main Results:

• Phylogenetically conserved hairpins, including the RSE, are crucial for efficient -1 PRF.
• Mutations in the RSE and LS significantly impact frameshifting levels.
• The LS structure can adopt alternative conformations, influencing frameshifting.
• Long-distance RNA-RNA interactions are less critical when LS structure is stabilized.
• Deletion of an upstream hairpin dramatically increases frameshifting in the absence of the RSE.

Conclusions:

• The RSE and its associated structures play a critical role in modulating -1 PRF efficiency.
• RNA secondary structure stability and conformational flexibility are key regulatory factors.
• Mechanisms may exist to suppress frameshifting when the RSE is not optimally structured.
• Understanding these regulatory elements is vital for viral translation control.