A translational enhancer derived from tobacco mosaic virus is functionally equivalent to a Shine-Dalgarno sequence.

Abstract

When present at the 5' end of mRNAs, the untranslated leader sequence (omega) of tobacco mosaic virus RNA significantly enhances translation in eukaryotes and prokaryotes. We have tested a deletion derivative of the omega sequence, omega delta 3, for its enhancing ability on gene constructs in which the ribosomal binding site was either present or deleted, in several Gram-negative bacterial species including Escherichia coli, Agrobacterium tumefaciens, Xanthomonas campestris pv. vitians, Erwinia amylovora, and Salmonella typhimurium. In vivo production of chloramphenicol acetyltransferase from a gene construct lacking its native ribosomal binding site was enhanced 40- to 120-fold by the presence of omega delta 3. Similar levels of enhancement (30- to 240-fold) were observed when the gene encoding beta-glucuronidase was tested. With a chloramphenicol acetyltransferase construct containing a ribosomal binding site, enhancement was markedly less, between 1- and 3.8-fold. Omega delta 3 appeared to enhance translation independent of its position upstream of the AUG codon used for initiation.