Fig. 1.

Examples of non-canonical translational mechanisms utilized by RNA viruses. Canonical eukaryotic mRNA translation is shown in the top panel. Red arrows indicate initiation of protein synthesis (at the start of an ORF) or continuation of translation by 80S ribosomes, with thicker arrows indicating the predominant path taken by ribosomes (not to scale). Green arrows indicate the probable movement of 40S subunits in a non-canonical manner. Where two distinct polypeptides are synthesized, the ORFs are shown in different shades of blue; where a recoding event during elongation leads to C-terminal extension of a polypeptide, the two ORFs are shown in the same colour. In the stop–carry on mechanism, both termination and initiation steps are non-canonical, as indicated by the red square and green circle.