ATP-dependent RNA helicase involved in pre-spliceosome/complex A assembly and mRNA splicing (PubMed:14713954). Bridges U1 and U2 snRNPs during pre-spliceosome assembly and enables stable U2 snRNP association with intron RNA (PubMed:14713954). Through its helicase activity probably catalyzes an ATP-dependent conformational change of U2 snRNP (PubMed:14713954). ATP + H2O = ADP + H(+) + phosphate The Q motif is unique to and characteristic of the DEAD box family of RNA helicases and controls ATP binding and hydrolysis. Belongs to the DEAD box helicase family. DDX46/PRP5 subfamily.