title: Identification and characterization of a novel non-structural protein of bluetongue virus.
abstract: Bluetongue virus (BTV) is the causative agent of a major disease of livestock (bluetongue). For over two decades, it has been widely accepted that the 10 segments of the dsRNA genome of BTV encode for 7 structural and 3 non-structural proteins. The non-structural proteins (NS1, NS2, NS3/NS3a) play different key roles during the viral replication cycle. In this study we show that BTV expresses a fourth non-structural protein (that we designated NS4) encoded by an open reading frame in segment 9 overlapping the open reading frame encoding VP6. NS4 is 77-79 amino acid residues in length and highly conserved among several BTV serotypes/strains. NS4 was expressed early post-infection and localized in the nucleoli of BTV infected cells. By reverse genetics, we showed that NS4 is dispensable for BTV replication in vitro, both in mammalian and insect cells, and does not affect viral virulence in murine models of bluetongue infection. Interestingly, NS4 conferred a replication advantage to BTV-8, but not to BTV-1, in cells in an interferon (IFN)-induced antiviral state. However, the BTV-1 NS4 conferred a replication advantage both to a BTV-8 reassortant containing the entire segment 9 of BTV-1 and to a BTV-8 mutant with the NS4 identical to the homologous BTV-1 protein. Collectively, this study suggests that NS4 plays an important role in virus-host interaction and is one of the mechanisms played, at least by BTV-8, to counteract the antiviral response of the host. In addition, the distinct nucleolar localization of NS4, being expressed by a virus that replicates exclusively in the cytoplasm, offers new avenues to investigate the multiple roles played by the nucleolus in the biology of the cell.
authors.affiliation: MRC-University of Glasgow Centre for Virus Research, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Maxime
authors.initials: M
authors.lastname: Ratinier
authors.forename: Marco
authors.initials: M
authors.lastname: Caporale
authors.forename: Matthew
authors.initials: M
authors.lastname: Golder
authors.forename: Giulia
authors.initials: G
authors.lastname: Franzoni
authors.forename: Kathryn
authors.initials: K
authors.lastname: Allan
authors.forename: Sandro Filipe
authors.initials: SF
authors.lastname: Nunes
authors.forename: Alessia
authors.initials: A
authors.lastname: Armezzani
authors.forename: Amr
authors.initials: A
authors.lastname: Bayoumy
authors.forename: Frazer
authors.initials: F
authors.lastname: Rixon
authors.forename: Andrew
authors.initials: A
authors.lastname: Shaw
authors.forename: Massimo
authors.initials: M
authors.lastname: Palmarini
mesh_terms: D000818:Animals; D001819:Bluetongue / Q000235:genetics / Q000378:metabolism*; D001820:Bluetongue virus / Q000502:physiology*; D002460:Cell Line; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism / Q000821:virology; D006224:Cricetinae; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism / Q000821:virology; D004195:Disease Models, Animal; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D051379:Mice; D016366:Open Reading Frames / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000096:biosynthesis* / Q000235:genetics; D014779:Virus Replication / Q000502:physiology*
chemical_list: D017361:Viral Nonstructural Proteins