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Linear double-stranded RNA genome and non-enveloped
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sedoreovirinae
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spinareovirinae
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60 to 85 nm
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dsRNA
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11 segments
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size of genome - 10 - 27 kb
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6 structural proteins
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VP1
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RdRp
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VP2
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Core protein
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VP3
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Guanylyltransferase
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VP4
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spike protein - cleaves VP5 and VP8
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VP6
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Intermediate capsid
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VP7
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neutralization of Ag
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6 Non-structural protein
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NSP1
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Interferon antagonist
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NSP2
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NTPase - viroplasms with NSP5
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NSP3
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Translation enhancer
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NSP4
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Viroporins
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NSP5
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Viroplasms with NSP2
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NSP6
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Interacts with NSP5
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Efficient replication requires cleavage of the outer capsid spike protein VP4, which allows the structurally flexible spike protein, VP4, to undergo conformational changes to interact with a series of cellular receptors.
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The virus is internalized by receptor-mediated endocytosis. The low calcium of the endosome releases outer capsid VP7 trimers, resulting in a conformational change in the VP4 spike protein that releases the transcriptionally active double-layered particles into the cytoplasm.
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Viral messenger RNAs (mRNAs) are used to translate proteins and as templates for RNA genome replication and packaging into newly made double-layered particles (DLPs) that occurs in specialized structures called viroplasms that co-localize and require components of lipid droplets for formation.
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Triple-layered particle (TLP) assembly is completed by a unique process involving binding of newly made DLPs to NSP4 that serves as an intracellular receptor, followed by particles budding into the endoplasmic reticulum
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During this process, transient enveloped particles are seen, the outer capsid proteins VP4 and VP7 are assembled, and the transient envelope is lost.
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The viral glycoproteins do not traffic to the Golgi. In polarized epithelial cells, particles are released both by viral lysis and by a nonclassical vesicular transport mechanism.
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