An RNA stem-loop structure involved in the packaging of bovine leukemia virus genomic RNA in vivo

An RNA secondary structure of the bovine leukemia virus (BLV) 5'-terminal RNA sequence was constructed by computer-assisted RNA secondary structure analysis. Mutations were created in the noncoding region (NCR) of BLV, which contains a conserved consensus sequence, to disrupt predicted secondary structure of this region. After transfection of these constructs into FLK-BLV cells and analysis of viral particles a reduction in mutant RNA content was observed relative to that of unmutated vector RNA. The packaging efficiency of the mutant with a substitution in the consensus sequence was reduced threefold and that of the mutant with a deleted 5' NCR was reduced fivefold. We conclude that predicted RNA secondary structure and/or nucleotide sequence of the BLV noncoding region is essential for BLV RNA packaging in vivo.