A family of conserved noncoding elements derived from an ancient transposable element

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Abstract
The evolutionary origin of the conserved noncoding elements (CNEs) in the human genome remains poorly understood but may hold important clues to their biological functions. Here, we report the discovery of a CNE family with approximately 124 instances in the human genome that demonstrates a clear signature of having been derived from an ancient transposon. The CNE family is also present in the chicken genome, although typically not at orthologous locations. The CNE family is closely related to the active transposon SINE3 in zebrafish and also to a previously uncharacterized transposon in the coelacanth, the so-called "living fossil" belonging to the lobe-finned fish lineage. The mammal, bird, zebrafish, and coelacanth families all share a highly similar core element of approximately 180 bp but have important differences in their 5' and 3' ends. The core element has thus been preserved over 450 million years of evolution, implying an important biological function. In addition, we identify 95 additional CNE families that likely predate the mammalian radiation. The results highlight both the creative role of transposons and the importance of CNE families.