title: Nonstructural Protein NSs of Schmallenberg Virus Is Targeted to the Nucleolus and Induces Nucleolar Disorganization.
abstract: Schmallenberg virus (SBV) was discovered in Germany in late 2011 and then spread rapidly to many European countries. SBV is an orthobunyavirus that causes abortion and congenital abnormalities in ruminants. A virus-encoded nonstructural protein, termed NSs, is a major virulence factor of SBV, and it is known to promote the degradation of Rpb1, a subunit of the RNA polymerase II (Pol II) complex, and therefore hampers global cellular transcription. In this study, we found that NSs is mainly localized in the nucleus of infected cells and specifically appears to target the nucleolus through a nucleolar localization signal (NoLS) localized between residues 33 and 51 of the protein. NSs colocalizes with nucleolar markers such as B23 (nucleophosmin) and fibrillarin. We observed that in SBV-infected cells, B23 undergoes a nucleolus-to-nucleoplasm redistribution, evocative of virus-induced nucleolar disruption. In contrast, the nucleolar pattern of B23 was unchanged upon infection with an SBV recombinant mutant with NSs lacking the NoLS motif (SBVΔNoLS). Interestingly, unlike wild-type SBV, the inhibitory activity of SBVΔNoLS toward RNA Pol II transcription is impaired. Overall, our results suggest that a putative link exists between NSs-induced nucleolar disruption and its inhibitory function on cellular transcription, which consequently precludes the cellular antiviral response and/or induces cell death.
  
  
  OBJECTIVE
  Schmallenberg virus (SBV) is an emerging arbovirus of ruminants that spread in Europe between 2011 and 2013. SBV induces fetal abnormalities during gestation, with the central nervous system being one of the most affected organs. The virus-encoded NSs protein acts as a virulence factor by impairing host cell transcription. Here, we show that NSs contains a nucleolar localization signal (NoLS) and induces disorganization of the nucleolus. The NoLS motif in the SBV NSs is absolutely necessary for virus-induced inhibition of cellular transcription. To our knowledge, this is the first report of nucleolar functions for NSs within the Bunyaviridae family.
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Julie
authors: J
authors: Gouzil
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Aurore
authors: A
authors: Fablet
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Estelle
authors: E
authors: Lara
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Grégory
authors: G
authors: Caignard
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Marielle
authors: M
authors: Cochet
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Cindy
authors: C
authors: Kundlacz
authors: MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom.
authors: Massimo
authors: M
authors: Palmarini
authors: MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom.
authors: Mariana
authors: M
authors: Varela
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Emmanuel
authors: E
authors: Breard
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Corinne
authors: C
authors: Sailleau
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Cyril
authors: C
authors: Viarouge
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Muriel
authors: M
authors: Coulpier
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Stéphan
authors: S
authors: Zientara
authors: ANSES, UMR1161 Virologie, Laboratory for Animal Health, Maisons-Alfort, France damien.vitour@vet-alfort.fr.|INRA, UMR1161, Maisons-Alfort, France.|Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR1161 Virologie, Maisons-Alfort, France.
authors: Damien
authors: D
authors: Vitour
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D002466:Cell Nucleolus / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D002831:Choroid Plexus / Q000166:cytology / Q000378:metabolism / Q000821:virology; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D063928:Ependymoglial Cells / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000090243:Nucleophosmin; D016851:Orthobunyavirus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D021382:Protein Sorting Signals; D021381:Protein Transport; D059748:Proteolysis; D012319:RNA Polymerase II / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012756:Sheep; D015398:Signal Transduction; D014158:Transcription, Genetic; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D002868:Chromosomal Proteins, Non-Histone; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D017361:Viral Nonstructural Proteins; C047458:fibrillarin; D000090243:Nucleophosmin; D012319:RNA Polymerase II
keywords: Cellular shutoff; NSs; Schmallenberg virus; bunyavirus; nucleolus