ATP-binding RNA helicase involved in the biogenesis of 60S ribosomal subunits. Binds 90S pre-ribosomal particles and dissociates from pre-60S ribosomal particles after processing of 27SB pre-rRNA. Required for the normal formation of 18S rRNA through the processing of pre-rRNAs at sites A0, A1 and A2, and the normal formation of 25S and 5.8S rRNAs through the processing of pre-rRNAs at sites C1 and C2. ATP + H2O = ADP + H(+) + phosphate Component of pre-60S ribosomal complexes. 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. DDX55/SPB4 subfamily.