As an RNA helicase, unwinds RNA and alters RNA structures through ATP binding and hydrolysis. Involved in multiple cellular processes, including pre-mRNA splicing, alternative splicing, rRNA processing and miRNA processing, as well as transcription regulation (By similarity) (PubMed:12368261). Plays a role in innate immunity. Specifically restricts bunyavirus infection, including Rift Valley fever virus (RVFV) or La Crosse virus (LACV), but not vesicular stomatitis virus (VSV), in an interferon- and DROSHA-independent manner (PubMed:25126784). ATP + H2O = ADP + H(+) + phosphate Interacts with Fmr1 to form the RNA-induced silencing complex (RISC), a ribonucleoprotein (RNP) complex involved in translation regulation, other components of the complex are RpL5, RpL11, AGO2 and Dcr-1. In the course of bunyavirus infection, relocalizes from the nucleus to the cytosol where it binds viral RNA to antagonize replication. No phenotype under normal conditions. Upon infection with Rift Valley fever virus (RVFV) or La Crosse virus (LACV), knockdown flies exhibit increased mortality. No phenotype upon infection with other viruses, including vesicular stomatitis virus (VSV), Sindbis virus (SINV), nor Drosophila C virus (DCV). Belongs to the DEAD box helicase family. DDX5/DBP2 subfamily.