Long terminal repeat retrotransposons jump between species.

Abstract

Retrotransposons are an evolutionarily ancient class of mobile genetic elements that transpose replicatively within their host genomes via RNA intermediates. There are three major retrotransposon groups, the Ty1-copia group and the gypsy group long terminal repeat (LTR) retrotransposons and the non-LTR retrotransposons or LINE elements (ref. 1; Fig. 1). All three groups are widespread in the eukaryotes, although none of the LTR retrotransposon groups have been detected in mammals or birds as yet. All LTR retrotransposons share striking sequence similarities with the retroviruses of vertebrates, and at least one LTR retrotransposon of Drosophila is in fact an infectious retrovirus (2). It is universally believed that modern day retroviruses, LTR retrotransposons, and non-LTR retrotransposons share a common ancestor, though there is some dispute about which came first (1, 3, 4).