Notes on Family: Metaviridae
variable ovoid or spheroid
This family contains retroelements that produce virus-like particles (VLPs). They do not share the infectivity of 'true' viruses but the VLP stage appears to be an essential stage in their 'life cycle'. VLPs contain the RNA intermediate and the corresponding DNA is integrated into the host genome. These properties are shared by members of the family Pseudoviridae
but the genomic oranisation is different, with the integrase gene downstream of the reverse transcriptase.
Virus-like particles (VLPs) are poorly studied but seem to include irregular ovoid enveloped particles up to 100 nm in diameter.
The major molecule is a positive sense ssRNA transcript of 4-11 kb flanked by Long Terminal Repeats (LTRs).
Genera in the Family
The genera are based on distinct lineages in phylogenetic analyses of their reverse transcriptase domains:
- Errantivirus: Genomes >6 kb with 3 ORFs
- Metavirus: Genomes <6 kb with 1 or 2 ORFs
- Semotivirus: Genomes from 4 to >10 kb with 1-3 ORFs; distantly related to the other genera