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Conservation of ancient full-length open reading frames in vertebrate endogenous retroviruses
Retrovirology volume 8, Article number: P47 (2011)
Endogenous retroviruses (ERVs) are genetic remnants of exogenous retroviral infections that have endured selective processes and made their way into ancestral host genomes. While many of them have deteriorated beyond the ability to code for detectable proteins, some still retain activity or the potential for coding activity [1–3]. A few active ERVs have been coopted into fully functional genes that play important roles in development or disease [1, 2, 4]. New high throughput data revealed that these ERVs are far more common than previously thought and different software packages have been created to search genomes for these structures. In this study, we build on such a tool to look at several vertebrate genomes, search for ERV remnants and identify loci with long, intact open reading frames for the major retroviral genes and dating these loci of interest using the long terminal repeat (LTR) divergence method .
Materials and methods
The genomes of twelve vertebrates were acquired from UCSC Genome Browser and analyzed with an in-house method based on the Itrharvest software package, complemented with additional filtering and data retrieval. Candidate ERV loci were then probed for full-length open reading frames, which were classified within one of the three major retroviral genes: gag, pol or env by a BlastX  against a retroviral protein database. LTR dating for each ERV locus was done by comparing the genetic divergence between the LTRs.
Our study reveals the existence of a few conserved full length open reading frames in loci whose LTRs present a similarity lower than 70% and plenty of open reading frames occur across all genomes in loci with LTR similarity below 80%. Current method limitations may cause this number to be an underestimation but nonetheless reveals the existence of old retroviral infections that have, to this date, kept some coding potential. In the studied primate genomes, a select number of loci still retain long to full length open reading frames on all three major genes even on loci with LTR divergence under 95% (Table 1). Pol genes appear to possess the highest number of conserved ORF and a high number of recent integrations with full conservation has been found in the mouse genome.
Simpson GR, et al: Endogenous D-type (HERV-K) related sequences are packaged into retroviral particles in the placenta and possess open reading frames for reverse transcriptase. Virology. 1996, 222: 451-456. 10.1006/viro.1996.0443.
Mi S, et al: Syncytin, a captured retroviral envelope protein involved in human placental morphogenesis. Nature. 2000, 403: 785-789. 10.1038/35001608.
Takeuchi Y, et al: Host range and interference studies of three classes of pig endogenous retrovirus. J Virol. 1998, 72: 9986-9991.
Nexø BA, et al: The etiology of multiple sclerosis: genetic evidence for the involvement of the human endogenous retrovirus HERV-Fc1. PLoS One. 2011, 6 (2): e16652-10.1371/journal.pone.0016652.
SanMiguel P, et al: The paleontology of intergene retrotransposons of maize. Nat Genet. 1998, 20: 43-45. 10.1038/1695.
Ellinghaus D: LTRharvest, an efficient and flexible software for de novo detection of LTR retrotransposons. BMC Bioinf. 2008, 9: 18-10.1186/1471-2105-9-18.
Altschul SF, et al: Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Res. 1997, 25: 3389-3402. 10.1093/nar/25.17.3389.
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Cite this article
Martins, H., Villesen, P. Conservation of ancient full-length open reading frames in vertebrate endogenous retroviruses. Retrovirology 8, P47 (2011) doi:10.1186/1742-4690-8-S2-P47
- Long Terminal Repeat
- UCSC Genome Browser
- Code Activity
- Vertebrate Genome
- High Throughput Data