ATP-dependent RNA helicase. Binds to partially double-stranded RNAs (dsRNAs) in order to unwind RNA secondary structures. Unwinding is promoted in the presence of single-strand binding proteins. Mediates also RNA duplex formation thereby displacing the single-strand RNA binding protein. ATP and ADP modulate its activity: ATP binding and hydrolysis by DDX42 triggers RNA strand separation, whereas the ADP-bound form of the protein triggers annealing of complementary RNA strands. Involved in the survival of cells by interacting with TP53BP2 and thereby counteracting the apoptosis-stimulating activity of TP53BP2. Relocalizes TP53BP2 to the cytoplasm. ATP + H2O = ADP + H(+) + phosphate Component of splicing factor SF3B complex which is composed of at least eight subunits; SF3B1, SF3B2, SF3B3, SF3B4, SF3B5, SF3B6, PHF5A/SF3B14B, and DDX42/SF3B125. Interacts (via the C-terminus) with TP53BP2; the interaction is not inhibitied by TP53BP2 ubiquitination and is independent of p53/TP53. Expressed in several cell lines (at protein level). Expressed in liver, lung, tonsil, thymus, muscle and pancreatic islets. Belongs to the DEAD box helicase family. DDX42 subfamily.