Intruder (DD38E), a recently evolved sibling family of DD34E/Tc1 transposons in animals

Abstract

AbstractBackgroundA family ofTc1/marinertransposons with a characteristic DD38E triad of catalytic amino acid residues, namedIntruder(IT), was previously discovered in sturgeon genomes, but their evolutionary landscapes remain largely unknown.ResultsHere, we comprehensively investigated the evolutionary profiles ofITs, and evaluated their cut-and-paste activities in cells.ITsexhibited a narrow taxonomic distribution pattern in the animal kingdom, with invasions into two invertebrate phyla (Arthropoda and Cnidaria) and three vertebrate lineages (Actinopterygii, Agnatha, and Anura): very similar to that of the DD36E/ICfamily. Some animal orders and species seem to be more hospitable toTc1/marinertransposons, one order of Amphibia and seven Actinopterygian orders are the most common orders with horizontal transfer events and have been invaded by all four families (DD38E/IT, DD35E/TR, DD36E/ICand DD37E/TRT) ofTc1/marinertransposons, and eight Actinopterygii species were identified as the major hosts of these families. IntactITshave a total length of 1.5–1.7 kb containing a transposase gene flanked by terminal inverted repeats (TIRs). The phylogenetic tree and sequence identity showed thatITtransposases were most closely related to DD34E/Tc1.ITshave been involved in multiple events of horizontal transfer in vertebrates and have invaded most lineages recently (< 5 million years ago) based on insertion age analysis. Accordingly,ITspresented high average sequence identity (86–95%) across most vertebrate species, suggesting that some are putatively active.ITs can transpose in human HeLa cells, and the transposition efficiency of consensus TIRs was higher than that of the TIRs of natural isolates.ConclusionsWe conclude that DD38E/IToriginated from DD34E/Tc1and can be detected in two invertebrate phyla (Arthropoda and Cnidaria), and in three vertebrate lineages (Actinopterygii, Agnatha and Anura).IThas experienced multiple HT events in animals, dominated by recent amplifications in most species and has high identity among vertebrate taxa. Our reconstructedITtransposon vector designed according to the sequence from the “cat” genome showed high cut-and-paste activity. The data suggest thatIThas been acquired recently and is active in many species. This study is meaningful for understanding the evolution of theTc1/marinersuperfamily members and their hosts.