Discovery of amphibian Tc1-like transposon families.

We have discovered transposase sequences in the bull frog (Rana catesbeiana) and in the clawed frog (Xenopus laevis), which demonstrates that there are DNA-mediated transposons in Amphibia. The DNA sequences of 11 new Xenopus elements describe two new vertebrate transposon families. Phylogenetic analysis, using these sequences along with previously defined vertebrate and invertebrate elements, reveals at least five families of Tc1-like elements in Vertebrata. Some of these families co-exist in the same genome. Furthermore, the grouping of one of the amphibian transposon families with a branch of the teleost transposons raises the possibility of horizontal transfer.