Tymovirus (taxid:12148)

VIRION

The virion is non-enveloped and contains an isometric capsid with T=3 icosahedral symmetry, measuring about 30 nm in diameter. The capsid is built from proteins adopting a single jelly-roll fold.

GENOME

Linear, C-rich, ssRNA(+) genome of 6.3 kb. The 3'-terminus has a tRNA-like structure.

GENE EXPRESSION

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.

ENZYMES

• RNA-dependent RNA polymerase [Polyprotein]
• Alpha-type capping [Polyprotein]
• Polyprotein major protease (Peptidase C21) [Polyprotein]

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.
8. Movement protein allows cell-to-cell movement.

Host-virus interaction

Modulation of host ubiquitin pathway by virus

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