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

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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.