The complete nucleotide sequence of RNA2 of stunt virus (HaSV), a member of the , was determined by characterization of cloned cDNA and PCR products and direct sequencing of genomic RNA. The capped, positive sense, single-stranded RNA is 2478 nucleotides in length and has two overlapping open reading frames (ORFs) likely to be cistrons which are situated between terminal non-coding regions of 282 and 168 bases, 5′ and 3′, respectively. Extensive secondary structure of the RNA strand is indicated, including a tRNA-like structure at the 3′ terminus which is the first such structure discerned in an animal virus. The first ORF encodes a 17 kDa PEST protein (p17) of unknown function while the second ORF encodes the 71 kDa coat protein precursor (p71) that is cleaved at an Asn-Phe site into the 64 kDa and 7 kDa coat proteins. The precursor coat protein is 66% identical to that of another tetravirus, the ω virus, with most of the difference residing in a 165 amino acid region located in the middle of the sequence. Despite the extensive similarity, no serological relationship was observed between the two viruses, suggesting that the dissimilar region is exposed on the capsid exterior. Expression in bacteria of the two RNA2 gene products shows they are likely to be expressed by a leaky scan-through mechanism. Bacterial expression of p71 did not produce virus-like particles while expression of p17 produced large arrays of mostly hollow, hexagonal tube-like structures.


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