title: The amino terminus of the salmonid alphavirus capsid protein determines subcellular localization and inhibits cellular proliferation.
abstract: Salmonid alphavirus (SAV) is the most divergent member of the family Togaviridae and constitutes a threat to farming of salmonid fish in Europe. Here, we report cloning, expression and preliminary functional analysis of the capsid protein of SAV, confirming it to be expressed as an approximately 31-kDa protein in infected cells. The protein localizes strictly to the cytoplasm in Chinook salmon embryo cells, and either to the nucleus or cytoplasm in bluegill fry cells. An expression study of full-length and different truncated versions of the SAV capsid fused to the enhanced green fluorescent protein demonstrated that the localization is independent of other viral components in both cell lines, and controlled by the N-terminal 82 aa, which include a conserved, predicted helix and a downstream positively charged region. Thus, the results suggest that the SAV capsid possesses a cell-type-dependent potential for nuclear import and export. Moreover, the SAV capsid and its N-terminal 82 aa were shown to be associated with inhibition of cellular proliferation, a hallmark of the cytopathic effect caused by SAV. These results highlight that the SAV capsid is a multifunctional protein with possible importance for pathogenesis.
authors.affiliation: Department of Biology, University of Bergen, Thor Møhlens gate 55, 5020 Bergen, Norway. marius.karlsen@bio.uib.no
authors.forename: Marius
authors.initials: M
authors.lastname: Karlsen
authors.forename: Muhammed Naveed
authors.initials: MN
authors.lastname: Yousaf
authors.forename: Stephane
authors.initials: S
authors.lastname: Villoing
authors.forename: Are
authors.initials: A
authors.lastname: Nylund
authors.forename: Espen
authors.initials: E
authors.lastname: Rimstad
mesh_terms: D000524:Alphavirus / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects*; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D054884:Host-Pathogen Interactions; D010802:Phylogeny; D012487:Salmonidae / Q000821:virology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013347:Subcellular Fractions / Q000378:metabolism*
chemical_list: D036022:Capsid Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins