Efficient ribosome binding of brome mosaic virus (BMV) RNA4 contributes to its ability to outcompete the other BMV RNAs for translation.

Analysis of translation products synthesized in vitro in the presence of a mixture of brome mosaic virus (BMV) RNAs 1, 2, 3, and 4 usually shows a predominance of coat protein, coded by RNA4. The proportion of products directed by RNAs 1 and 2 decreased at saturating concentrations of BMV RNA and in the presence of 7-methylguanosine 5'-phosphate (m7G5'p) at nonsaturating concentrations of RNA. No differences in the relative proportions of the various proteins produced were detected in the presence of T-2 toxin, which interferes with the formation of the first peptidyl bond rather than competing for initiation factor, as has been suggested for m7G5'p. These data show that the ability of BMV RNA4 to outcompete BMV RNAs 1, 2, and 3 results, at least in part, from its ability to bind more efficiently to ribosomes.