NUCLEOTIDE-SEQUENCE AND GENOMIC ORGANIZATION OF ACYRTHOSIPHON-PISUM VIRUS

The nucleotide sequence of the genomic RNA of Acyrthosiphon pisum viru s was determined. The APV genome is 10,016 nucleotides in length, excl uding the 3'-end poly(A) track, and contains two large open reading fr ames (ORFs), encoding proteins of 296,340 and 63,279 Da. The ORF1 is p receded by an untranslated leader sequence of 267 nucleotides. The ORF 1 product contains sequence motifs characteristic of RNA-dependent RNA polymerases, chymotrypsin-like proteases, and helicases. Interviral s equence comparison revealed significant similarities with viruses belo nging to the so-called picornavirus superfamily. The ORF2 is most like ly expressed by a -1 translational frameshift and is followed by an un translated sequence of 222 nucleotides. Internal amino acid sequences of three capsid proteins (66K, 34K, 23/24K) were determined. Compariso n of the obtained amino acid sequences with the APV sequence disclosed that the structural proteins are located in the 3'-terminal half of t he genome. The 34K protein is encoded by the ORF1, while the 66K prote in contains both ORF1-(34K) and ORF2-derived sequences and is probably expressed by a translational frameshift The 23/24K proteins mast like ly arise by proteolytic breakdown of the 34K protein. Although the ded uced APV genomic organization in some aspects resembles that of the pi cornaviruses, its overall genomic organization indicates that APV is a distinct species only distantly related to the Picornaviridae. (C) 19 97 Academic Press.