A ribosome-bound pseudoknot in the HCV coding region stimulates viral growth by tuning viral translation.

Recent studies have uncovered a number of functional RNA structures in RNA viruses, yet their regulatory roles remain poorly understood. Here, using an unbiased proteomic approach alongside targeted biochemical assays, we investigate a previously uncharacterized functional pseudoknot (pk1) within the hepatitis C virus coding region and show that it stably interacts with host ribosomes, inhibiting translation and potentially acting as a regulator between viral translation and RNA genome replication. Comparative structural analysis identifies pk1-like elements in related RNA viruses, suggesting a conserved regulatory mechanism. This study expands the known functions of pseudoknots in viral coding regions beyond frameshifting, highlights the critical role of RNA structure-mediated regulation within viral open reading frames, and provides insight into the design of viral therapeutics and vaccines.