title: Characterization of Striped jack nervous necrosis virus subgenomic RNA3 and biological activities of its encoded protein B2.
abstract: Striped jack nervous necrosis virus (SJNNV), which infects fish, is the type species of the genus Betanodavirus. This virus has a bipartite genome of positive-strand RNAs, designated RNAs 1 and 2. A small RNA (ca. 0.4 kb) has been detected from SJNNV-infected cells, which was newly synthesized and corresponded to the 3'-terminal region of RNA1. Rapid amplification of cDNA ends analysis showed that the 5' end of this small RNA (designated RNA3) initiated at nt 2730 of the corresponding RNA1 sequence and contained a 5' cap structure. Substitution of the first nucleotide of the subgenomic RNA sequence within RNA1 selectively inhibited production of the positive-strand RNA3 but not of the negative-strand RNA3, which suggests that RNA3 may be synthesized via a premature termination model. The single RNA3-encoded protein (designated protein B2) was expressed in Escherichia coli, purified and used to immunize a rabbit to obtain an anti-protein B2 polyclonal antibody. An immunological test showed that the antigen was specifically detected in the central nervous system and retina of infected striped jack larvae (Pseudocaranx dentex), and in the cytoplasm of infected cultured E-11 cells. These results indicate that SJNNV produces subgenomic RNA3 from RNA1 and synthesizes protein B2 during virus multiplication, as reported for alphanodaviruses. In addition, an Agrobacterium co-infiltration assay established in transgenic plants that express green fluorescent protein showed that SJNNV protein B2 has a potent RNA silencing-suppression activity, as discovered for the protein B2 of insect-infecting alphanodaviruses.
authors.affiliation: Kamiura Station, Japan Fisheries Research Agency, Oita 879-2602, Japan.
authors.forename: Tokinori
authors.initials: T
authors.lastname: Iwamoto
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Mise
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takeda
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, 739-8528, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okinaka
authors.affiliation: Kamiura Station, Japan Fisheries Research Agency, Oita 879-2602, Japan.
authors.forename: Koh-Ichiro
authors.initials: KI
authors.lastname: Mori
authors.affiliation: Kamiura Station, Japan Fisheries Research Agency, Oita 879-2602, Japan.
authors.forename: Misao
authors.initials: M
authors.lastname: Arimoto
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Okuno
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima, 739-8528, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nakai
mesh_terms: D000818:Animals; D005393:Fish Diseases / Q000821:virology; D005399:Fishes / Q000821:virology; D016679:Genome, Viral; D030381:Nodaviridae / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics* / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase