An essential fifth coding ORF in the sobemoviruses
The sobemoviruses have one of the smallest of all known RNA (ribonucleic acid) virus genomes
Abstract
The sobemoviruses have one of the smallest of all known RNA virus genomes. ORF1 encodes P1 which plays a role in suppression of silencing and virus movement, ORFs 2a and 2b encode the replicational polyproteins P2a and P2ab, and ORF3 encodes the coat protein. Translation of ORF2a from the genomic RNA is dependent on a leaky scanning mechanism.
The authors report the presence of an additional ORF (ORFx), conserved in all sobemoviruses. ORFx overlaps the 5′ end of ORF2a in the +2 reading frame and also extends some distance upstream of ORF2a. ORFx lacks an AUG initiation codon and its expression is predicted to depend on low level initiation at near-cognate non-AUG codons, such as CUG, by a proportion of the ribosomes that are scanning the region between the ORF1 and ORF2a initiation codons. Mutations that disrupt translation of ORFx in turnip rosette virus prevent the establishment of infection.
This work arises from the Sustainable Crop production for International Development (SCPRID) programme.
Citation
Ling R, Pate A, Carr J, Firth A (2013). An essential fifth coding ORF in the sobemoviruses. Virology. 446(1-2): 397-408