Role of the RNA2 3′ non-translated region of Blackcurrant reversion nepovirus in translational regulation

The 3 ' non-translated regions (NTRs) of mRNAs of eukaryotes and their viruses often contain translational enhancers (TEs). Blackcurrant reversion nepovirus (BRV) has a genome composed of two uncapped polyadenylated RNAs with very long 3 ' NTRs, nucleotide sequences of which are very conserved between different BRV isolates. In this work, we studied a role of the RNA2 3 ' NTR in translation, using mutagenesis of the firefly luciferase reporter mRNA, in protoplasts of Nicotiana benthamiana. The RNA2 3 ' NTR was found to contain a cap-independent TE (3 ' CITE), which must base pair with the 5 ' NTR to facilitate translation. The BRV 3 ' CITE and poly(A) tail provided a major contribution to translational efficiency, with less input from other 3 ' NTR parts. The BRV 3 ' CITE does not share similarity in nucleotide sequence and secondary structure with other viruses and thus represents a new class of 3 ' CITE. (c) 2006 Elsevier Inc. All rights reserved.