February 17th, 2009. Even in evolution there can be too much of a good thing. What if a transposon broke free and replicated whenever it wanted to, and integrated wherever it wanted to, unchecked? How long would the host be around?
Such may have happened to Alu repeats in primates about 40 million years ago. Yet lucky for it, miRNA targeting the Alu got caught up in the binge and held on for the ride. The Alu sequences flanked the miRNA sequences, so when Alu replicated its designated driver was there to take the keys.
Or so speculate a group of Belgian researchers studying the largest primate-specific miRNA cluster, found on human chromosome 19. C19MC seems to be made up of multiple duplications of a cassette composed of four Alu repeats and one miRNA whose seed sequence targets the most conserved sequences of the Alu transposon. Join the fun at PLoS One, February 2009