ATP-binding RNA helicase involved in translation initiation. Remodels RNA in response to ADP and ATP concentrations by facilitating disruption, but also formation of RNA duplexes. Has weak ATP-dependent affinity for dsRNA, but strong ATP-dependent affinity for ssRNA. Acts as a virus host factor involved in the replication of the MBV and the L-A viruses by promoting the negative-strand RNA synthesis. May be involved in recognition of the preinitiation complex and DNA binding of the RNA polymerase III and play a role in mRNA splicing. ATP + H2O = ADP + H(+) + phosphate Interacts with the L-A virus GAG protein and the whole L-A virus particles. 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. DDX3/DED1 subfamily.