An active non-LTR retrotransposon with tandem structure in the compact genome of the pufferfish Tetraodon nigroviridis.
The fish retrotransposable element Zebulon encodes a reverse transcriptase and a carboxy-terminal restriction enzyme-like endonuclease, and is related phylogenetically to site-specific non-LTR retrotransposons from nematodes. Zebulon was detected in the pufferfishes Tetraodon nigroviridis and Takifugu rubripes, as well as in the zebrafish Danio rerio. Structural analysis suggested that Zebulon, in contrast to most non-LTR retrotransposons, might be able to retrotranspose as a partial tandem array. Zebulon was active relatively recently in the compact genome of T. nigroviridis, in which it contributed to the extension of intergenic and intronic sequences, and possibly to the formation of genomic rearrangements. Accumulation of Zebulon together with other retrotransposons was observed in some heterochromatic chromosomal regions of the genome of T. nigroviridis that might serve as reservoirs for active elements. Hence, pufferfish compact genomes are not evolutionarily inert and contain active retrotransposons, suggesting the presence of mechanisms allowing accumulation of retrotransposable elements in heterochromatin, but minimizing their impact on euchromatic regions. Homologous recombination between partial tandem sequences eliminating active copies of Zebulon and reducing the size of insertions in intronic and intragenic regions might represent such a mechanism.
Bouneau
Laurence
L
Genoscope/Centre National de Séquençage and CNRS-UMR 8030, F-91057 Evry Cedex 06, France.
Fischer
Cécile
C
Ozouf-Costaz
Catherine
C
Froschauer
Alexander
A
Jaillon
Olivier
O
Coutanceau
Jean-Pierre
JP
Körting
Cornelia
C
Weissenbach
Jean
J
Bernot
Alain
A
Volff
Jean-Nicolas
JN
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D016384:Consensus Sequence / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D015321:Gene Rearrangement / Q000235:genetics; D016678:Genome; D006570:Heterochromatin / Q000235:genetics; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009348:Nematoda / Q000235:genetics; D010802:Phylogeny; D018626:Retroelements / Q000235:genetics*; D013045:Species Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*; D020079:Terminal Repeat Sequences / Q000235:genetics*; D023721:Tetraodontiformes / Q000235:genetics*
D021901:DNA, Intergenic; D006570:Heterochromatin; D018626:Retroelements