Tymoviridae

VIRION

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Non-enveloped, isometric capsid with T=3 icosahedral symmetry, about 30 nm in diameter.
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GENOME

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Monopartite, linear, C-rich, ssRNA(+) genome of 6-7.5 kb. The 3'-terminus may have a tRNA-like structure or a polyA tract, depending upon the virus.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. The virion RNA is infectious and serves as both the genome and viral messenger RNA. The ORF1 encodes a polyprotein whichis expressed by leaky scanning. The capsid protein is translated from a subgenomic RNA.

REPLICATION

CYTOPLASMIC

  1. Virus penetrates into the host cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. The viral RNA is translated to produce the protein necessary for RNA synthesis (replication and transcription).
  4. Replication occurs in viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. The RdRp recognizes an internal subgenomic promoter on the negative-sense RNA to transcribe the 3'co-terminal subgenomic RNA that will generate the capsid protein.
  7. Assembly of new virus particles.

Host-virus interaction

Modulation of host ubiquitin pathway by virus

Turnip yellow mosaic virus 98K replication protein counteracts degradation of its RNA-dependent RNA polymerase (RdRp) by the host ubiquitin-proteasome system. The viral 98K replication protein mediates deubiquitylation of RdRp leading to its stabilization .