NeSL-1, an ancient lineage of site-specific non-LTR retrotransposons from Caenorhabditis elegans.
Phylogenetic analyses of non-LTR retrotransposons suggest that all elements can be divided into 11 lineages. The 3 oldest lineages show target site specificity for unique locations in the genome and encode an endonuclease with an active site similar to certain restriction enzymes. The more "modern" non-LTR lineages possess an apurinic endonuclease-like domain and generally lack site specificity. The genome sequence of Caenorhabditis elegans reveals the presence of a non-LTR retrotransposon that resembles the older elements, in that it contains a single open reading frame with a carboxyl-terminal restriction-like endonuclease domain. Located near the N-terminal end of the ORF is a cysteine protease domain not found in any other non-LTR element. The N2 strain of C. elegans appears to contain only one full-length and several 5' truncated copies of this element. The elements specifically insert in the Spliced leader-1 genes; hence the element has been named NeSL-1 (Nematode Spliced Leader-1). Phylogenetic analysis confirms that NeSL-1 branches very early in the non-LTR lineage and that it represents a 12th lineage of non-LTR elements. The target specificity of NeSL-1 for the spliced leader exons and the similarity of its structure to that of R2 elements leads to a simple model for its expression and retrotransposition.
Malik
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HS
Department of Biology, University of Rochester, Rochester, New York 14627-0211, USA.
Eickbush
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TH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D018509:DNA, Helminth; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D012326:RNA Splicing; D018626:Retroelements / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D020079:Terminal Repeat Sequences
D018509:DNA, Helminth; D018626:Retroelements