MOLECULAR-CLONING AND SEQUENCING OF THE CAPSID AND THE NUCLEAR INCLUSION PROTEIN GENES OF A NORTH-AMERICAN PVYN ISOLATE

The sequence of the 3'-terminal 3258 nucleotides of a tobacco veinal n ecrosis strain of a potato virus Y (PVYN) isolate from North America w as determined. The sequence revealed an open reading frame of 2931 nuc leotides, of which the start codon was not identified. The nontranslat ed region contains 327 nucleotides upstream of a poly(A) tract. The op en reading frame encodes a large polyprotein containing 976 amino acid s. The data indicate that the coat protein (CP) and the nuclear inclus ion protein (NIb) are derived from the large polypeptide by proteolyti c cleavage similar to many other potyviruses. The putative cleavage si tes of NIa/NIb and NIb/CP correspond to Q/A and Q/G sequences, respect ively, as in other PVYN isolates. The CP and NIb contain 267 and 519 a mino acid residues, respectively. Higher sequence homology of CP was o bserved with other PVYN isolates than with the PVYO isolates.