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 Mr 25,749 (ORF2), Mr 11,435 (ORF3), Mr 6984 (ORF4), the triple gene block proteins, a protein Mr 34,638 (ORF5); the coat protein, and a protein of Mr 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 Mr 16,817. 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.