An Intact Retroviral Gene Conserved in Spiny-Rayed Fishes for over 100 My

Mol Biol Evol. 2017 Mar 1;34(3):634-639. doi: 10.1093/molbev/msw262.


We have identified a retroviral envelope gene with a complete, intact open reading frame (ORF) in 20 species of spiny-rayed fishes (Acanthomorpha). The taxonomic distribution of the gene, "percomORF", indicates insertion into the ancestral lineage >110 Ma, making it the oldest known conserved gene of viral origin in a vertebrate genome. Underscoring its ancient provenence, percomORF exists as an isolated ORF within the intron of a widely conserved host gene, with no discernible proviral sequence nearby. Despite its remarkable age, percomORF retains canonical features of a retroviral glycoprotein, and tests for selection strongly suggest cooption for a host function. Retroviral envelope genes have been coopted for a role in placentogenesis by numerous lineages of mammals, including eutherians and marsupials, representing a variety of placental structures. Therefore percomORF's presence within the group Percomorpha-unique among spiny-finned fishes in having evolved placentation and live birth-is especially intriguing.

Keywords: endogenous retrovirus; evolution.; viral gene cooption.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biological Evolution
  • Conserved Sequence
  • Endogenous Retroviruses / genetics*
  • Evolution, Molecular
  • Fishes / genetics*
  • Fishes / virology*
  • Gene Products, env / genetics*
  • Open Reading Frames
  • Phylogeny
  • Proviruses / genetics
  • Retroviridae Proteins / genetics
  • Sequence Analysis, DNA / methods
  • Viral Envelope Proteins / genetics


  • Gene Products, env
  • Retroviridae Proteins
  • Viral Envelope Proteins