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Type Species |
(DmeGypV) |
Expression of DmeGypV results in production of enveloped irregular particles of approximately 100 nm in diameter and also much smaller non-enveloped particles. The env gene predicts a protein of Mr 54 
103. The actual protein has an apparent Mr of 66 103 and is N-glycosylated as indicated by susceptibility to endoglycosidase F. More rapidly migrating molecules of 54 and 28 103 are also observed and are inferred to result from proteolytic processing by host enzymes, as in the case of members of the family Retroviridae.
Genome Organization and Replication
DmeGypV is 7469 bp in length including two LTRs of 482 bp. It differs from most retroviruses and retrotransposons in that the termini are composed of AG . . . TT rather than TG . . . CA. The 11 nts immediately adjacent to the upstream U3 element and overlapping by one nt is complementary to tRNALys. The DNA flanking the insertion includes 4 bp repeats and the insertion site preference is for YRYRYR (where Y = purine and R = pyrimidine) sequence. The genomic RNA contains one ORF encoding major structural protein and a second ORF overlapping in the -1 frame, encoding homologues of retroviral PR, RT and IN. A third ORF, env, encoding a 54 103 envelope protein occurs in a spliced 2.1 kb mRNA. This protein is apparently N-glycosylated and processed into smaller species. This protein is analogous to retroviral envelope proteins by virtue of hydrophobic putative membrane spanning domains, localization to the viral membrane, similarity of processing sites for cleavage into trans-membrane and surface domains, and glycosylation. An envelope protein has been identified for Drosophila ananassae Tom virus (DanTomV) and is inferred from the composition of the third ORF of the other insect elements Drosophila melanogaster 17.6 virus (Dme176V) and Drosophila melanogaster 297 virus (Dme297V).
DmeGypV is transcribed into a 6.5 kb genomic RNA. A minus-strand strong stop species of approximately 242 nts (with RNA removed) has been identified. Plus-strand strong-stop DNA species of 479 nts which are similar in length to the LTR and a species longer by 15 to 18 nts presumed to result from copying of the tRNA primer have been observed.
DmeGypV transposition is repressed by the activity of the flamenco gene. In females homozygous for the permissive allele of flam, the somatic follicle cells surrounding maternal germline cells appear to accumulate DmeGypV RNA and envelope protein; Transposition, however, is observed in the maternal germ cells, and this has lead to the hypothesis that transposition is attributable to infection from surrounding follicle cells. Infection has been demonstrated to result when susceptible strains are raised in the presence of DmeGypV particles mixed into their food. Incubation with antibodies against the env protein decreased the level of infection, implicating env in this process.
List of Species Demarcation Criteria in the Genus
Individual species in the genus all have less than 50% identity in their Gag protein sequences compared to all other species. For example Dme297V and DmeGypV are two relatively closely related species of elements in this family from Drosophila melanogaster, but their Gag sequences are only 35% identical.
Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:
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Caenorhabditis elegans Cer1 virus |
[U15406] |
(CelCer1V) |
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Drosophila ananassae Tom virus |
[Z24451] |
(DanTomV) |
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Drosophila melanogaster 17.6 virus |
[X01472] |
(Dme176V) |
|
Drosophila melanogaster 297 virus |
[X03431] |
(Dme297V) |
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Drosophila melanogaster gypsy virus |
(DmeGypV) | |
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(Drosophila melanogaster mdg4 virus) |
[M12927] |
|
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Trichoplusia ni TED virus |
[M32662] |
(TniTedV) |
Tentative Species in the Genus
None reported.
List of Unassigned Species in the Family
|
Drosophila virilis Penelope virus |
[U49102] |
(DviPenV) |
Phylogenetic Relationships within the Family
See Fig. 2.
At least one member of this group, DmeGypV, is infectious, and all members of the genus Errantivirus have a third ORF resembling env. This makes them candidates for inclusion into the family Retroviridae rather than the family Metaviridae. However, examination of phylogenetic trees based on reverse transcriptase coding sequences (Fig. 2, and see also Fig. 4 in the family Pseudoviridae) places these elements squarely in the family Metaviridae. Reverse transcriptase amino acid sequences are the most conserved sequences in retroelements and hence are the best character on which to base such trees.
Erranti: from Latin errans “to wander”.
Meta: from Greek metathesis for “transposition”. Also to connote some uncertainty as to whether these are true viruses or not.
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