VIRAL EDITORS. “Persistent viral infection events most probably determine gene word order in both prokaryotes and eukaryotes. A variety of examples demonstrate that these viral colonizers are still active in specific developmental processes in that they are expressed in a rather limited developmental window until the process is finished. Then they are regulatory silenced again.”
http://jmcb.oxfordjournals.org/content/early/2011/03/31/jmcb.mjr005.full