Molecular Mechanisms for the RNA-Dependent ATPase Activity of Upf1 and Its Regulation by Upf2

► Upf1 binds RNA at an extended channel with nanomolar affinity ► The Upf1 CH domain promotes RNA binding allosterically via conformational changes ► Binding of Upf2 reduces the extent of RNA binding by Upf1 ► In the absence of the CH domain, RNA binding is decreased and unwinding is enhanced