Evolution and phylogeny of insect endogenous retroviruses.
BACKGROUND
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. 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.


RESULTS
To 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.


CONCLUSIONS
We 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.
Terzian
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IGH-CNRS, 141 rue de la Cardonille, Montpellier, France. christophe.terzian@igh.cnrs.fr
Pélisson
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Bucheton
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D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D033622:Ceratitis capitata / Q000201:enzymology / Q000821:virology*; D030541:Databases, Genetic; D004330:Drosophila / Q000201:enzymology / Q000821:virology*; D004331:Drosophila melanogaster / Q000201:enzymology / Q000821:virology*; D020077:Endogenous Retroviruses / Q000201:enzymology / Q000235:genetics*; D019143:Evolution, Molecular; D015686:Gene Products, env / Q000737:chemistry / Q000235:genetics; D015683:Gene Products, gag / Q000737:chemistry / Q000235:genetics; D015684:Gene Products, pol / Q000737:chemistry / Q000235:genetics; D007304:Insect Viruses / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D018626:Retroelements / Q000235:genetics; D016914:Ribonuclease H / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics
D015686:Gene Products, env; D015683:Gene Products, gag; D015684:Gene Products, pol; D018626:Retroelements; D014759:Viral Envelope Proteins; D012194:RNA-Directed DNA Polymerase; D016914:Ribonuclease H