NUCLEOTIDE-SEQUENCE AND GENE ORGANIZATION OF THE 3'-TERMINAL REGION OF CHRYSANTHEMUM VIRUS-B GENOMIC RNA

DNA clones complementary to the 3'-terminal 3426 nucleotides of the genomic RNA of the carlavirus chrysanthemum virus B (CVB) have been sequenced. The sequence contains six open reading frames (ORFs) which encode putative proteins (in the 5' --> 3' direction) of M(r) 25 749 (ORF2), M(r) 11 435 (ORF3), M(r) 6984 (ORF4), the triple gene block proteins, a protein M(r) 34638 (ORF5); the coat protein, and a protein of M(r) 12 609 (ORF6). The latter protein is basic and contains a putative zinc finger motif The 5'-proximal ORF1 encodes a product with substantial homology to the C-terminal portions of the putative RNA replicases of two other carlaviruses, potato viruses M and S. The analysis of the minus-sense sequence shows one ORF which encodes a polypeptide of M(r) 16817. The sequenced portion of the CVB genomic RNA contains three short internal non-coding regions, two of which are typical for carlaviruses (those between ORFs 1 and 2, and between ORFs 4 and 5), and one (between ORFs 5 and 6) is unusual. There is significant similarity in the amino acid sequences of the CVB RNA-encoded proteins and the corresponding proteins of other carlaviruses.