To estimate the timing of transposition, we scored presence/absence across related vespertilionid genome sequences with estimated divergence times.
At a time of high Alu transposition activity, Alu facilitated growth of the miRNA cluster, which by its targeting properties influenced the life cycle of Alu so that duplication rates declined.
In this article, we propose to quantify transposition activity over time from the distribution of transposition events.
Again, it's not the most original chord progression – this time a transposition of Neil Young's My My Hey Hey (Into the Blue) – but it's a slow-building masterpiece of desperation.
Our working hypothesis was that newly transposed EhSINE1s would be identical in sequence to the parent copy and would have easily-recognisable TSDs, but that over time these similarities would decay, providing a rough measure of time since transposition.
Intermediate situations are also plausible, namely, that the frequency, time line, and downstream consequences of transposition may vary with the triggering event, cell type, tissue, or some other parameter.
Since two LTRs of a single LTR retrotransposon have identical sequences at the time of integration, dating the transposition event of a LTR retrotransposon can be achieved reliably by computing the sequence similarity of its two LTRs [ 13].
These various (non-mutually exclusive) types of copies may provide information on how MLEs decay over time; i.e., through loss of transposition ability or loss of activity.
The number of TEs fixed under relaxed selection in small populations is determined primarily by the rate of transposition and the time during which the elements were active [ 27- 29]. Figure 1 schematically illustrates a hypothetical splitting of a large population, with a pool of active TEs, into small subpopulations that inherit either some of the active TEs, or none.
Here we have looked in more detail at one member of this group of elements and shown that it is possible to detect sub-populations that seem to have arisen from waves of transposition at different times in the past, and also shown that while present-day mobility cannot be demonstrated there is no evidence that it is not still occurring to some extent.
