title: Pns12 protein of Rice dwarf virus is essential for formation of viroplasms and nucleation of viral-assembly complexes.
abstract: Cytoplasmic inclusion bodies, known as viroplasms or viral factories, are assumed to be the sites of replication of members of the family Reoviridae. Immunocytochemical and biochemical analyses were carried out to characterize the poorly understood viroplasms of the phytoreovirus Rice dwarf virus (RDV). Within 6 h of inoculation of cells, viroplasms, namely discrete cytoplasmic inclusions, were formed that contained the non-structural proteins Pns6, Pns11 and Pns12 of RDV, which appeared to be the constituents of the inclusions. Formation of similar inclusions in non-host insect cells upon expression of Pns12 in a baculovirus system and the association of molecules of Pns12 in vitro suggested that the inclusions observed in RDV-infected cells were composed basically of Pns12. Core proteins P1, P3, P5 and P7 and core virus particles were identified in the interior region of the inclusions. In contrast, accumulation of the outer capsid proteins P2, P8 and P9 and of intact virus particles was evident in the peripheral regions of the inclusions. These observations suggest that core particles were constructed inside the inclusions, whereas outer capsid proteins were assembled at the periphery of the inclusions. Viral inclusions were shown to be the sites of viral RNA synthesis by labelling infected cells with 5-bromouridine 5'-triphosphate. The number of viroplasms decreased with time post-inoculation as their sizes increased, suggesting that inclusions might fuse with one another during the virus-propagation process. Our results are consistent with a model, proposed for vertebrate reoviruses, in which viroplasms play a pivotal role in virus assembly.
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Taiyun
authors.initials: T
authors.lastname: Wei
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Kyoji
authors.initials: K
authors.lastname: Hagiwara
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kikuchi
authors.affiliation: Faculty of Agriculture, Ibaraki University, Ami, Ibaraki 300-0332, Japan.|Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Moriyasu
authors.affiliation: Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Suzuki
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Chen
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Omura
mesh_terms: D000818:Animals; D002460:Cell Line; D002479:Inclusion Bodies / Q000821:virology*; D012275:Oryza / Q000821:virology*; D012367:RNA, Viral / Q000235:genetics; D012087:Reoviridae / Q000235:genetics / Q000502:physiology*; D017361:Viral Nonstructural Proteins / Q000032:analysis / Q000378:metabolism*; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D012367:RNA, Viral; D017361:Viral Nonstructural Proteins