The majority of the changes at the WSJ over the past 3 years (Murdoch bought the paper in the summer of 2007) can only be understood in terms of positioning the paper as a NYT-killer.
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 gene silencing (PTGS).
Even today in the world of satellite based GPS and the fairly exact positioning information it can provide, it is always best to have a paper chart or map and the needed tools in case your electronic ones fail so you are not left stranded and unable to find your way home.