title: Infectious Salmon Anaemia Virus (ISAV) RNA Binding Protein Encoded by Segment 8 ORF2 and Its Interaction with ISAV and Intracellular Proteins.
abstract: Infectious salmon anaemia virus (ISAV) is an orthomyxovirus infecting salmonid fish. The virus is adapted to low temperature and has a replication optimum between 10-15 °C. In this study the subcellular localization and protein interactions for the protein encoded by the largest open reading frame of gene segment 8 (s8ORF2) were investigated. In ISAV infected cells the s8ORF2 protein was found mainly in the cytosol but a minor fraction of cells expressed the protein in the nucleus as well. Green fluorescent protein-tagged s8ORF2 did not leak out of the cell when the plasma membrane was permeabilized, suggesting interactions with intracellular structural components. The s8ORF2 protein exists both as monomer and homodimer, and co-immunoprecipitation experiments strongly suggests it binds to the ISAV fusion-, nucleo- and matrix proteins. Two versions of s8ORF2 were detected with apparent molecular weights of 24-26 and 35 kDa in lysates of infected cells. The 35 kDa type is an early viral protein while the smaller version appears during the later phases of infection. The 24-26 kDa type was also the predominant form in viral particles. The s8ORF2 protein has previously been shown to bind RNA and interfere with interferon induction and signaling. Here we found that a fraction of the s8ORF2 protein pool in infected cells is likely to be conjugated to the interferon stimulated gene 15 (ISG15) and ubiquitin. Furthermore, several endogenous proteins pulled down by the s8ORF2 protein were identified by liquid chromatography mass spectrometry (LC-MS).
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Food Safety &amp; Infection Biology, Norwegian University of Life Sciences (NMBU), 0454 Oslo, Norway. christel.olsen@gmail.com.
authors.forename: Christel M
authors.initials: CM
authors.lastname: Olsen
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Food Safety &amp; Infection Biology, Norwegian University of Life Sciences (NMBU), 0454 Oslo, Norway. turhan.markussen@nmbu.no.
authors.forename: Turhan
authors.initials: T
authors.lastname: Markussen
authors.affiliation: Department of Biosciences, P.O. Box 1066 Blindern, University of Oslo, 0316 Oslo, Norway. bernd.thiede@ibv.uio.no.
authors.forename: Bernd
authors.initials: B
authors.lastname: Thiede
authors.affiliation: Faculty of Veterinary Medicine and Biosciences, Department of Food Safety &amp; Infection Biology, Norwegian University of Life Sciences (NMBU), 0454 Oslo, Norway. espen.rimstad@nmbu.no.
authors.forename: Espen
authors.initials: E
authors.lastname: Rimstad
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D009975:Orthomyxoviridae / Q000235:genetics / Q000378:metabolism*; D009976:Orthomyxoviridae Infections / Q000235:genetics / Q000378:metabolism / Q000662:veterinary* / Q000821:virology; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012474:Salmon / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D016601:RNA-Binding Proteins; D014764:Viral Proteins
keywords: ISAV; ISG15; LC-MS; biscistronic; gene segment 8; infectious salmon anaemia virus; orthomyxovirus; ubiquitin