Tepovirus

VIRION

Non-enveloped, slightly flexuous, filamentous, 640 nm or more long and 12 nm in diameter.

GENOME

Linear ssRNA(+) genome of 6.5 kb in size. The 3' terminus is polyadenylated. Encodes 3 proteins.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. Replication-related proteins are translated directly from the genomic RNA (ORF1). ORF2 and ORF3 are transcribed presumably as subgenomic mRNAs (sgRNAs) and respectively code for the movement and capsid protein.

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 as a monocistronic mRNA to produce the RdRp (encoded by the 5'-proximal ORF).
  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. Internal subgenomic promoters are used to transcribe the sgRNAs. Traduction of these sgRNAs yields the capsid and movement proteins.
  7. Assembly of new virus particles.
  8. Movement protein allows cell-to-cell and long-distance movement.