A novel endogenous retrovirus-related element in the human genome resembles a DNA transposon: evidence for an evolutionary link?

Abstract

A significant fraction of the human genome is composed of various types of transposable elements, which are divided into two broad classes based on their mehcanism of transposition: via an RNA intermediate (retroelements) or via a DNA intermediate (DNA transposons). The retroelements, which include endogenous retroviruses, are the more prominent group in humans and seem to be restricted to eukaryotes. DNA transposons are known in almost all well-studied organisms, including bacteria. In the human genome, they exist as mere fossils and seem to have been inactive for millions of years. We report here an element in the human genome that is the product of a recent retrotransposition event, yet apparently, by a novel mechanism of reverse transcription, has acquired inverted repeats more characteristic of DNA transposons.