Cotranslational folding stimulates programmed ribosomal frameshifting in the alphavirus structural polyprotein

Area of Science:

• Molecular Biology
• Virology
• Biophysics

Background:

• Viruses utilize programmed ribosomal frameshifting (PRF) to maximize coding capacity, producing multiple proteins from a single mRNA.
• PRF is typically induced by mRNA structural elements creating tension between the transcript and ribosome.

Purpose of the Study:

• To investigate the role of cotranslational polypeptide folding in stimulating PRF.
• To demonstrate that forces generated by nascent polypeptide chain conformation can enhance PRF.

Main Methods:

• Biochemical assays
• Cellular studies
• Computational modeling (coarse-grained molecular dynamics simulations)
• Analysis of Sindbis virus structural polyprotein biosynthesis

Main Results:

• Sindbis virus polyprotein forms two competing topological isomers during biosynthesis.
• Formation of one topological isomer is directly linked to PRF.
• Translocon-mediated membrane integration generates force on the nascent chain, correlating with frameshifting levels.

Conclusions:

• Cotranslational folding of the viral protein generates tension that stimulates PRF.
• This is the first demonstration linking nascent polypeptide chain conformation to PRF.
• Suggests cotranslational folding/binding events may broadly stimulate PRF beyond RNA-mediated mechanisms.