The paper in PNAS suggests that the actual positioning of the motifs is associated with small RNA molecules that are involved with a process called post-transcriptional genesilencing (PTGS).
"The caution is that this is not going to explain even 1% of what these conserved regions are, " cautions David Bartel of MIT's Whitehead Institute, who has done much of the work on genesilencing.
Now a similar sea change may be afoot, thanks to a new technology called RNA interference, or RNAi, which allows scientists to stop a disease by silencing a particular gene.