title: The Specific Requirements for CR1 Retrotransposition Explain the Scarcity of Retrogenes in Birds.
abstract: 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.
authors.affiliation: Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden, alexander.suh@ebc.uu.se.
authors.forename: Alexander
authors.initials: A
authors.lastname: Suh
mesh_terms: D000489:Alligators and Crocodiles / Q000235:genetics; D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000235:genetics*; D002645:Chickens / Q000235:genetics; D017124:Conserved Sequence; D055029:Inverted Repeat Sequences; D018895:Microsatellite Repeats; D010802:Phylogeny; D018626:Retroelements / Q000235:genetics*; D014426:Turtles / Q000235:genetics
chemical_list: D018626:Retroelements