ATP-dependent RNA helicase involved spliceosome assembly and in nuclear splicing. Catalyzes an ATP-dependent conformational change of U2 snRNP. Bridges U1 and U2 snRNPs and enables stable U2 snRNP association with intron RNA. ATP + H2O = ADP + H(+) + phosphate Interacts with the U2 snRNP and HSH155. The Q motif is unique to and characteristic of the DEAD box family of RNA helicases and controls ATP binding and hydrolysis. Present with 358 molecules/cell in log phase SD medium. Belongs to the DEAD box helicase family. DDX46/PRP5 subfamily.