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Review
. 2018 Nov 20;19(11):3653.
doi: 10.3390/ijms19113653.

Rex Retroelements and Teleost Genomes: An Overview

Federica Carducci  1 , Marco Barucca  2 , Adriana Canapa  3 , Maria Assunta Biscotti  4
Affiliations
Review

Rex Retroelements and Teleost Genomes: An Overview

Federica Carducci et al. Int J Mol Sci. .

Abstract

Repetitive DNA is an intriguing portion of the genome still not completely discovered and shows a high variability in terms of sequence, genomic organization, and evolutionary mode. On the basis of the genomic organization, it includes satellite DNAs, which are organized as long arrays of head-to-tail linked repeats, and transposable elements, which are dispersed throughout the genome. These repeated elements represent a considerable fraction of vertebrate genomes contributing significantly in species evolution. In this review, we focus our attention on Rex1, Rex3 and Rex6, three elements specific of teleost genomes. We report an overview of data available on these retroelements highlighting their significative impact in chromatin and heterochromatin organization, in the differentiation of sex chromosomes, in the formation of supernumerary chromosomes, and in karyotype evolution in teleosts.

Keywords: repetitive DNA; retroelements; rex element; teleost; transposable elements.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Major divisions of repetitive DNA sequences in the eukaryotic genome. Transposable elements are widespread in the genome and are classified in Class I or Retroelements that require an RNA intermediated into the transposition mechanism and Class II or DNA transposons that move via DNA. Tandem repeats are made up of sequences organized in long array and, based on monomer size, minisatellites, microsatellites, and satellites are distinguishable.
Figure 2
Figure 2
Evolutionary relationships between jawless fishes, cartilaginous fishes, basal sarcopterygian fishes, and actinopterygians. Orange branch represents jawless fishes; green branch represents Chondrichthyes; blue branches represent Osteichthyes.
Figure 3
Figure 3
Main features of the Rex1 retroelement (A/P*, apurinic/apyrimidinic site that can be located upstream or downstream the RT-encoding region; RT, reverse transcriptase-encoding region; 3′UTR), Rex3 (EN, endonuclease-encoding region; TSD, target site duplication; RT, reverse transcriptase-encoding region; Ct, C-terminal domain–encoding region; tail consisting of tandem repeats of the sequence GCG (GAA)2 (GATG)n, where n = 8–17 [35], and Rex6 (RT, reverse transcriptase-encoding region; EN, endonuclease-encoding region).
See this image and copyright information in PMC

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