Abstract
BackgroundThe genome of invertebrates is rich in retroelements which are structurally reminiscent of the retroviruses of vertebrates. Those containing three open reading frames (ORFs), including an env-like gene, may well be considered as endogenous retroviruses. Further support to this similarity has been provided by the ability of the env-like gene of DmeGypV (the Gypsy endogenous retrovirus of Drosophila melanogaster) to promote infection of Drosophila cells by a pseudotyped vertebrate retrovirus vector.ResultsTo gain insights into their evolutionary story, a sample of thirteen insect endogenous retroviruses, which represents the largest sample analysed until now, was studied by computer-assisted comparison of the translated products of their gag, pol and env genes, as well as their LTR structural features. We found that the three phylogenetic trees based respectively on Gag, Pol and Env common motifs are congruent, which suggest a monophyletic origin for these elements.ConclusionsWe showed that most of the insect endogenous retroviruses belong to a major clade group which can be further divided into two main subgroups which also differ by the sequence of their primer binding sites (PBS). We propose to name IERV-K and IERV-S these two major subgroups of Insect Endogenous Retro Viruses (or Insect ERrantiVirus, according to the ICTV nomenclature) which respectively use Lys and Ser tRNAs to prime reverse transcription.
Highlights
The genome of invertebrates is rich in retroelements which are structurally reminiscent of the retroviruses of vertebrates
The sequences of thirteen insect endogenous retroviruses were included in this analysis, which represents the largest sample analysed until now
The primer binding sites (PBS) of insect endogenous retroviruses have unusual properties The insect endogenous retroviruses can be divided into two main groups: (DmeGypV DsuGypV DviGypV DmeNomV CcaYoyV) using a tRNALys and (Dme176V Dme297V DanTomV DmeZamV DmeTirV DmeIdeV DviTv1V TniTedV) using a tRNASer binding sites
Summary
The genome of invertebrates is rich in retroelements which are structurally reminiscent of the retroviruses of vertebrates Those containing three open reading frames (ORFs), including an env-like gene, may well be considered as endogenous retroviruses. Retrovirus-like elements have been found in the genomes of most Eukaryotes Their integrated/proviral forms consist of two long terminal repeats (LTRs) flanking an internal region which contains one to three major open reading frames (ORFs) coding for structural and enzymatic functions necessary for their replication cycle. Based on a phylogeny of their reverse transcriptase (RT) domains, the retrovirus-like elements were divided into two major groups: the Ty1/Copia and the Ty3/Gypsy families [1] They differ by the order of enzymatic domains encoded in the pol gene: Integrase – Reverse.
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