The specific requirements for CR1 retrotransposition explain the scarcity of retrogenes in birds

Alexander Suh

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21 Citations (Scopus)


Chicken repeat 1 (CR1) retroposons are the most abundant superfamily of transposable elements in the genomes of birds, crocodilians, and turtles. However, CR1 mobilization remains poorly understood. In this article, I document that the diverse CR1 lineages of land vertebrates share a highly conserved hairpin structure and an octamer microsatellite motif at their very 3′ ends. Together with the presence of these same motifs in the tails of CR1-mobilized short interspersed elements, this suggests that the minimum requirement for CR1 transcript recognition and retrotransposition is a complex >50-nt structure. Such a highly specific recognition sequence readily explains why CR1-dominated genomes generally contain very few retrogenes. Conversely, the mammalian richness in retrogenes results from CR1 extinction in their early evolution and subsequent establishment of L1 dominance.

Original languageEnglish
Pages (from-to)18-20
Number of pages3
JournalJournal of Molecular Evolution
Issue number1-2
Publication statusPublished - 20 Aug 2015


  • Chicken repeat 1
  • Land vertebrates
  • Long interspersed element
  • Microsatellite
  • Retrogene
  • Retrotransposition

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