genomic RNA

We have analysed the organization of the 3 ' end of the genomic RNA of canine coronavirus (CCV), a virus which has a close antigenic relationship to transmiss-ible gastroenteritis virus (TGEV), porcine respiratory coronavirus (PRCV) and feline infectious peritonitis virus (FIPV). Genomic RNA isolated from CCV strain Insavc-l-infected A72 cells was used to generate a cDNA library. Overlapping clones, spanning approxi-mately 9-6 kb [from the 3 ' end of the polymerase gene, lb, to the poly(A) tail] were identified. Sequencing and subsequent analyses revealed 10 open reading frames (ORFs). Three of these code for the major coronavirus structural polypeptides S,M and N; a fourth codes for a small membrane protein, SM, a putative homologue of the IBV structural polypeptide 3c, and five code for polypeptides, designated lb, 3a, 4, 7a and 7b, homolo-gous to putative non-structural polypeptides encoded in the TGEV or FIPV genomes. An extra ORF which had not hitherto been identified in this antigenic group of coronaviruses was designated 3x. Pairwise align-ment of these ORFs with their counterparts in TGEV, PRCV and FIPV revealed high levels of identity and highlighted the close relationship between the members of this group of viruses