An analysis by metabolic labelling of the encephalomyocarditis virus ribosomal frameshifting efficiency and stimulators

Abstract

Programmed 1 ribosomal frameshifting is a mechanism of gene expression whereby specific signals within messenger RNAs direct a proportion of ribosomes to shift 1 nt and continue translating in the new reading frame. Such frameshifting normally depends on an RNA structure stimulator 3′-adjacent to a ‘slippery’ heptanucleotide shift site sequence. Recently we identified an unusual frameshifting mechanism in encephalomyocarditis virus, where the stimulator involves a trans-acting virus protein. Thus, in contrast to other examples of 1 frameshifting, the efficiency of frameshifting in encephalomyocarditis virus is best studied in the context of virus infection. Here we use metabolic labelling to analyse the frameshifting efficiency of wild-type and mutant viruses. Confirming previous results, frameshifting depends on a G_GUU_UUU shift site sequence and a 3¢-adjacent stem-loop structure, but is not appreciably affected by the ‘StopGo’ sequence present ∼30 nt upstream. At late timepoints, frameshifting was estimated to be 46-76 % efficient.