The Complete Nucleotide Sequence of Avian Infectious Bronchitis Virus: Analysis of the Polymerase-Coding Region
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Avian infectious bronchitis virus (IBV) is the type species of the family Coronaviridae (Siddell et al., 1983). It has a large positive-stranded RNA genome which has been estimated at 20–24 kilobases (Lomniczi & Kennedy, 1977). As with other coronaviruses, a number of subgenomic messenger RNA species are produced in infected cells which form a 3′-coterminal nested set (Stern & Kennedy, 1980a; 1980b). In the case of IBV there are six mRNA species in total, which are designated mRNAs A-F, mRNA A being the smallest, and mRNA F being of genome size. mRNAs A, C and E encode the three main structural components of the virion, the nucleocapsid polypeptide, the membrane polypeptide and the precursor polypeptide to the spike (Stern & Sefton, 1984). mRNA D encodes at least one product, a 12.4 kilodalton polypeptide of unknown function (Smith et al., this volume), but no product has yet been detected for mRNA B. The coding regions of mRNAs A-E are situated in the 3′-most 7.3 kilobases of the IBV genome, the nucleotide sequence of which has been determined previously from cDNA clones (Boursnell et al., 1984, 1985a, 1985b; Boursnell & Brown, 1984; Binns et al., 1985b).
KeywordsCodon Usage Homology Region Vesicular Stomatitis Virus Infectious Bronchitis Virus Mouse Hepatitis Virus
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