Complex dynamics under tension in a high-efficiency frameshift stimulatory structure

Significance Programmed ribosomal frameshifting (PRF) is important to many viruses, but how structures in mRNA stimulate PRF remains uncertain. By studying a frameshift signal stimulating very high PRF in West Nile virus (WNV), we identify features that differ from other structures stimulating more modest PRF levels. Using single-molecule force spectroscopy to mimic the effects of tension applied to the RNA by the ribosome during translation, we find that the WNV frameshift signal exhibits exceptionally heterogeneous conformational dynamics, forming several different pseudoknots and multiple combinations of hairpins, all connected on 2 mutually exclusive pathways. This work supports a role for conformational heterogeneity in PRF, suggesting that dynamic fluctuations rather than static properties play a key role in stimulating PRF efficiently.