Genome-wide target site triplication of Alu elements in the human genome

article i nfo Alu elements are the most successful short interspersed elements in primate genomes and their retrotransposition is a major source of genomic expansion. Alu elements integrate into genomic regions through target-site primed reverse transcription, which generates target site duplications (TSDs). Unexpectedly, we have identified target site triplications (TSTs) at some loci, where two Alu elements in tandem share one direct repeat. Thus, the three copies of the repeat are present. We located 212 TST loci in the human genome and examined 25 putative human-specific TSTloci using PCR validation. As a result,12 human-specific TSTlociwereidentified.These findings