title: A polycistronic mRNA specified by the coronavirus infectious bronchitis virus.
abstract: The third largest of the nested set of subgenomic mRNAs (mRNA3) from the coronavirus infectious bronchitis virus (IBV) contains three separate open reading frames (3a, 3b, and 3c) which are not present on the next smallest of the mRNAs, suggesting that this mRNA may be functionally polycistronic. However, although a protein product has been identified from the 3c open reading frame, to date the coding function of 3a and 3b has not been established. We present nucleotide sequence data suggesting that each of the three open reading frames is conserved in a variety of different IBV strains and further show, through the preparation of monospecific antisera against bacterial fusion proteins, that IBV-infected cells contain small amounts of the products of these ORFs. In vitro translation studies using synthetic mRNAs containing the 3a, 3b, and 3c open reading frames suggest strongly that all three proteins can be translated from a single molecular species, and expression studies carried out in intact cells support this conclusion. Thus mRNA3 of IBV appears to be functionally tricistronic.
authors.affiliation: Department of Pathology, University of Cambridge, United Kingdom.
authors.forename: D X
authors.initials: DX
authors.lastname: Liu
authors.forename: D
authors.initials: D
authors.lastname: Cavanagh
authors.forename: P
authors.initials: P
authors.lastname: Green
authors.forename: S C
authors.initials: SC
authors.lastname: Inglis
mesh_terms: D000595:Amino Acid Sequence; D000956:Antigens, Viral / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D005814:Genes, Viral; D001351:Infectious bronchitis virus / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D015678:Viral Structural Proteins / Q000235:genetics
chemical_list: D000956:Antigens, Viral; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D015678:Viral Structural Proteins