IS481EU Shows a New Connection between Eukaryotic and Prokaryotic DNA Transposons.

DDD/E transposase gene is the most abundant gene in nature and many DNA transposons in all three domains of life use it for their transposition. A substantial number of eukaryotic DNA transposons show similarity to prokaryotic insertion sequences (ISs). The presence of IS-like DNA transposons was indicated in the genome of . Here, we surveyed IS-like eukaryotic sequences using a bioinformatics approach and report a group of eukaryotic IS-like DNA transposons, designated , from parabasalids including . The lengths of target site duplications (TSDs) of are around 4 bps, around 15 bps, or around 25 bps, and strikingly, these discrete lengths of TSDs can be observed even in a single family. Phylogenetic analysis indicated the close relationships of with some of the prokaryotic IS family members. was not well separated from / in the phylogenetic analysis, but was distinct from other eukaryotic DNA transposons including and . The unique characteristics of in protein sequences and the distribution of TSD lengths support its placement as a new superfamily of eukaryotic DNA transposons.