title: Discovery of a small arterivirus gene that overlaps the GP5 coding sequence and is important for virus production.
abstract: The arterivirus family (order Nidovirales) of single-stranded, positive-sense RNA viruses includes porcine respiratory and reproductive syndrome virus and equine arteritis virus (EAV). Their replicative enzymes are translated from their genomic RNA, while their seven structural proteins are encoded by a set of small, partially overlapping genes in the genomic 3'-proximal region. The latter are expressed via synthesis of a set of subgenomic mRNAs that, in general, are functionally monocistronic (except for a bicistronic mRNA encoding the E and GP2 proteins). ORF5, which encodes the major glycoprotein GP5, has been used extensively for phylogenetic analyses. However, an in-depth computational analysis now reveals the arterivirus-wide conservation of an additional AUG-initiated ORF, here termed ORF5a, that overlaps the 5' end of ORF5. The pattern of substitutions across sequence alignments indicated that ORF5a is subject to functional constraints at the amino acid level, while an analysis of substitutions at synonymous sites in ORF5 revealed a greatly reduced frequency of substitution in the portion of ORF5 that is overlapped by ORF5a. The 43-64 aa ORF5a protein and GP5 are probably expressed from the same subgenomic mRNA, via a translation initiation mechanism involving leaky ribosomal scanning. Inactivation of ORF5a expression by reverse genetics yielded a severely crippled EAV mutant, which displayed lower titres and a tiny plaque phenotype. These defects, which could be partially complemented in ORF5a-expressing cells, indicate that the novel protein, which may be the eighth structural protein of arteriviruses, is expressed and important for arterivirus infection.
authors.affiliation: Department of Pathology, University of Cambridge, Cambridge, UK.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Firth
authors.affiliation: Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jessika C
authors.initials: JC
authors.lastname: Zevenhoven-Dobbe
authors.affiliation: Department of Human Genetics, University of Utah, Salt Lake City, UT 84112-5330, USA.
authors.forename: Norma M
authors.initials: NM
authors.lastname: Wills
authors.affiliation: Department of Veterinary Science, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA.
authors.forename: Yun Young
authors.initials: YY
authors.lastname: Go
authors.affiliation: Department of Veterinary Science, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA.
authors.forename: Udeni B R
authors.initials: UBR
authors.lastname: Balasuriya
authors.affiliation: BioSciences Institute, University College Cork, Cork, Ireland.|Department of Human Genetics, University of Utah, Salt Lake City, UT 84112-5330, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Atkins
authors.affiliation: Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Snijder
authors.affiliation: Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Clara C
authors.initials: CC
authors.lastname: Posthuma
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000956:Antigens, Viral / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D007240:Equartevirus / Q000235:genetics*; D020868:Gene Silencing; D008969:Molecular Sequence Data; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014759:Viral Envelope Proteins / Q000235:genetics*; D010948:Viral Plaque Assay; D015678:Viral Structural Proteins / Q000235:genetics*; D014779:Virus Replication
chemical_list: D000956:Antigens, Viral; C550278:GP5 protein, equine arteritis virus; D014759:Viral Envelope Proteins; D015678:Viral Structural Proteins; C114789:glycoprotein 5, PRRSV