RNA pseudoknot domain of tobacco mosaic virus can functionally substitute for a poly(A) tail in plant and animal cells.

Abstract

The genomes of many RNA viruses terminate in a tertiary structure similar to the L-conformation of tRNAs and this structure is recognized by many tRNA-specific enzymes such as aminoacyl-tRNA synthetase. Virtually the entire 3'-untranslated region (UTR) of tobacco mosaic virus (TMV) RNA is involved in an extended tertiary structure containing, in addition to a tRNA-like structure, a pseudoknot domain that lies immediately upstream. Although the functions of these structures are not well understood, they are essential to the virus. We demonstrate that the addition of the 204-base TMV 3'-untranslated region to foreign mRNA constructs can increase gene expression up to 100-fold compared to nonadenylated mRNA. The 3'-UTR of TMV was equal to or greater than a polyadenylated tail in enhancing gene expression in electroporated dicot and monocot protoplasts. The TMV 3'-UTR is functionally similar to a polyadenylated tail in that it increases mRNA stability and translation and must be positioned at the 3' terminus to function efficiently. Similar effects on expression were observed in Chinese hamster ovary cells, demonstrating that the sequence functions in a wide range of eukaryotes. When the extended tertiary structure was dissected, the upstream pseudoknot domain was found to be largely responsible for increasing expression. The inclusion of the tRNA-like structure, however, was important for full regulation.

An RNA pseudoknot and an optimal heptameric shift site are required for highly efficient ribosomal frameshifting on a retroviral messenger RNA.

“…However, studies ofthe IBV frameshift site indicate that an extended simple stem-loop, equal in length to the two quasi-continuous helices in the pseudoknot, cannot replace the pseudoknot without loss of frameshifting efficiency (24). This implies that the pseudoknot has special features, beyond its predicted stability as deduced from base pairing, that may account for its role in frameshifting and other kinds of translational regulation (23,(35)(36)(37)(38)(39).…”

Replication of tobamovirus RNA

“…However, it has been shown that either deletion of the double-helical segment immediately upstream of the tRNA-like structure or a base substitution that destabilizes the helix results in loss of infectivity. 41) Gallie et al have demonstrated that this pseudoknot region enhances the translation of the genomic RNA, 42) which raises the possibility that the loss of infectivity is caused not only by defects in RNA replication, but also by reduced translation of the TMV-coded proteins. Although the host-encoded eukaryotic elongation factor 1A 43) and p102 (HSP101) 44), 45) have been shown to bind to the pseudoknot region, the importance of the interaction between the pseudoknot region and these proteins in the translation and replication of tobamovirus RNA have not been determined.…”

Ectopic Expression of Hel-N1, an RNA-Binding Protein, Increases Glucose Transporter (GLUT1) Expression in 3T3-L1 Adipocytes

“…The regulated stability of transferrin, granulocyte-macrophage colony-stimulating factor, and histone mRNAs has been shown, at least in part, to be controlled by the binding of specific proteins to consensus sequences in the 3Ј untranslated region (3ЈUTR) of these messages (3, 37, 41). Studies of tobacco mosaic virus, the Drosophila melanogaster developmental gene hunchback, human cytokine, and 15-lipoxygenase mRNAs have demonstrated that the 3ЈUTR also contains information capable of regulating translational efficiency which may be mediated by RNA-binding proteins (13,25,35,36). A major class of RNA-binding proteins which possess an 80-amino-acid consensus element, termed the RNA recognition motif (RRM) (39), which forms the core of a functional RNAbinding domain has been identified.…”