BOTH UAP56 AND URH49, WHICH FORM ESSENTIAL COMPLEXES FOR MRNA EXPORT, EVOLVED FROM A COMMON ANCESTRAL GENE. HOWEVER, THE DISTINCT ROLES THAT THESE COMPLEXES PLAY, AS WELL AS THE STRUCTURAL DIFFERENCES THAT GIVE RISE TO THESE EXCLUSIVE ROLES, ARE NOT WELL UNDERSTOOD. IN THIS STUDY, RESEARCHERS FOUND THAT THESE HELICASES ARE INVOLVED IN SEPARATE MRNA EXPORT PATHWAYS, AND THAT A CHANGE IN A SINGLE AMINO ACID BETWEEN UAP56 AND URH49 GIVES RISE TO MARKEDLY DIFFERENT ATP-UNBOUND (OR “APO-”) COMPLEXES.