ATP-dependent RNA helicase involved nonsense-mediated mRNA decay and ribosome biogenesis through rRNA processing (PubMed:11585918, PubMed:7883168). Associates directly with chromatin, correlating with transcriptional activity (PubMed:22679025). Required for assembly of mRNA-binding proteins YRA1, NAB2, and MEX67 onto poly(A)+ RNA (PubMed:23721653). ATP + H2O = ADP + H(+) + phosphate Interacts with UPF1. Associates with polysomes. The Q motif is unique to and characteristic of the DEAD box family of RNA helicases and controls ATP binding and hydrolysis. Results in defective assembly of nuclear mRNPs. Present with 33100 molecules/cell in log phase SD medium. The gene for DBP2 has an unusual intron both because of its size and because of its location near the 3' end of the gene. It may have a function in an intron-mediated negative feedback loop regulating DBP2 expression. Belongs to the DEAD box helicase family. DDX5/DBP2 subfamily.