ATP-dependent RNA helicase of the DEAD-box protein family; strong preference for dsRNA; remodels RNA-protein complex (RNP) to facilitate efficient transcription termination; required for assembly of Yra1p, Nab2p and Mex67p onto mRNA and formation of nuclear mRNP; involved in mRNA decay and rRNA processing; may be involved in suppression of transcription from cryptic initiation sites; promotes Mex67p-mediated nuclear export of mRNA by facilitating annealing with antisense RNAs to create dsRNAs