Fig. 2. Illustration of non-LTR retrotransposon insertion mechanisms.
TSDs are shown in green; AAAAA stands for polyA-tail; A) Illustrates a typical non-LTR retrotransposon insertion. These insertions are thought to occur via TPRT. The insertion is 3′ intact (contains a polyA-tail) and is flanked by TSDs. No host sequence is deleted. B) Shown are the typical hallmarks of an insertion-mediated deletion. The non-LTR retrotransposon is 3′ intact, indicated by the polyA-tail. TSDs are absent; upstream (left) of the element, host DNA is deleted. C) Illustrated is an endonuclease-independent insertion with deletion of host DNA 3′ and 5′ of the insertion. However, deletions can be limited to 3′ or 5′ host DNA sequence. The non-LTR retrotransposon usually does not contain a polyA-tail and is not flanked by TSDs.