Notes on Genus: Semotivirus

variable ovoid or spheroid
variable ovoid or spheroid

Type member: Ascaris lumbricoides Tas virus


General Description

This is one of the genera in the retroelement family Metaviridae. Members have 1 or 2 ORFs and are phylogenetically distant from the other genera. The name is from the Latin semotus = distant.


Virus-like particles (VLPs) are poorly studied but seem to include irregular ovoid enveloped particles up to 100 nm in diameter and smaller non-enveloped particles.


Positive sense, ssRNA molecules, 4-11 kb long, flanked by Long Terminal Repeats (LTRs).

Genus Genomic Organization

Genome organisation is variable with from 1 to 3 ORFs encoding the gag, pol and (sometimes) env proteins. Second and third ORFs (where present) are in separate reading frames and are translated by ribosomal frameshift. As in other genera of the family, the pol contains protease (PR), reverse transcriptase (RT) and integrase (IN) domains in that order.

Type Member Genomic Organization

The 3 overlapping ORFs are translated by ribosomal frameshift:
  1. gag: structural polyprotein of 71 kDa
  2. pol: polymerase of 120 kDa with protease (PR), reverse transcriptase (RT) and integrase (IN) domains
  3. env: envelope protein of 77 kDa