title: VP3 is crucial for the stability of Nora virus virions.
abstract: Nora virus is an enteric virus that causes persistent, non-pathological infection in Drosophila melanogaster. It replicates in the fly gut and is transmitted via the fecal-oral route. Nora virus has a single-stranded positive-sense RNA genome, which is translated in four open reading frames. Reading frame three encodes the VP3 protein, the structure and function of which we have investigated in this work. We have shown that VP3 is a trimer that has an α-helical secondary structure, with a functionally important coiled-coil domain. In order to identify the role of VP3 in the Nora virus life cycle, we constructed VP3-mutants using the cDNA clone of the virus. Our results show that VP3 does not have a role in the actual assembly of the virus particles, but virions that lack VP3 or harbor VP3 with a disrupted coiled coil domain are incapable of transmission via the fecal-oral route. Removing the region downstream of the putative coiled coil appears to have an effect on the fitness of the virus but does not hamper its replication or transmission. We also found that the VP3 protein and particularly the coiled coil domain are crucial for the stability of Nora virus virions when exposed to heat or proteases. Hence, we propose that VP3 is imperative to Nora virus virions as it confers stability to the viral capsid.
authors.affiliation: Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Sajna Anand
authors.initials: SA
authors.lastname: Sadanandan
authors.affiliation: Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden; Institute of Biomedical Technology, University of Tampere, FI-33520 Tampere, Finland.
authors.forename: Jens-Ola
authors.initials: JO
authors.lastname: Ekström
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Venkateswara Rao
authors.initials: VR
authors.lastname: Jonna
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Hofer
authors.affiliation: Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden; Institute of Biomedical Technology, University of Tampere, FI-33520 Tampere, Finland. Electronic address: dan.hultmark@umu.se.
authors.forename: Dan
authors.initials: D
authors.lastname: Hultmark
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D009154:Mutation; D000072756:Protein Conformation, alpha-Helical; D000072417:Protein Domains; D055503:Protein Multimerization; D012327:RNA Virus Infections / Q000635:transmission / Q000821:virology; D012328:RNA Viruses / Q000502:physiology*; D014771:Virion / Q000302:isolation & purification / Q000502:physiology*; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins
keywords: Capsid stability; Nora virus; RNA viruses; Virus biology