RNA helicase that acts as a sensor of the transcriptional status of both RNA polymerase (Pol) I and II: promotes ribosomal RNA (rRNA) processing and transcription from polymerase II (Pol II) (By similarity). Binds various RNAs, such as rRNAs, snoRNAs, 7SK and, at lower extent, mRNAs (By similarity). In the nucleolus, localizes to rDNA locus, where it directly binds rRNAs and snoRNAs, and promotes rRNA transcription, processing and modification (By similarity). Required for rRNA 2'-O-methylation, possibly by promoting the recruitment of late-acting snoRNAs SNORD56 and SNORD58 with pre-ribosomal complexes (By similarity). In the nucleoplasm, binds 7SK RNA and is recruited to the promoters of Pol II-transcribed genes: acts by facilitating the release of P-TEFb from inhibitory 7SK snRNP in a manner that is dependent on its helicase activity, thereby promoting transcription of its target genes (By similarity). Functions as cofactor for JUN-activated transcription: required for phosphorylation of JUN at 'Ser-77' (By similarity). Can unwind double-stranded RNA (helicase) and can fold or introduce a secondary structure to a single-stranded RNA (foldase) (By similarity). Together with SIRT7, required to prevent R-loop-associated DNA damage and transcription-associated genomic instability: deacetylation by SIRT7 activates the helicase activity, thereby overcoming R-loop-mediated stalling of RNA polymerases (By similarity). Involved in rRNA processing. May bind to specific miRNA hairpins (By similarity). Component of a multi-helicase-TICAM1 complex that acts as a cytoplasmic sensor of viral double-stranded RNA (dsRNA) and plays a role in the activation of a cascade of antiviral responses including the induction of pro-inflammatory cytokines via the adapter molecule TICAM1 (PubMed:21703541). ATP + H2O = ADP + H(+) + phosphate Acetylation inhibits the helicase activity. Homodimer; homodimerizes via its N-terminus (PubMed:21703541). Found in a multi-helicase-TICAM1 complex at least composed of DHX36, DDX1, DDX21 and TICAM1; this complex exists in resting cells with or without poly(I:C) RNA ligand stimulation (PubMed:21703541). Interacts (via C-terminus) with TICAM1 (via TIR domain) (PubMed:21703541). Interacts with DHX36 (via C-terminus); this interaction serves as bridges to TICAM1 (PubMed:21703541). Interacts (via C-terminus) with DDX1 (via B30.2/SPRY domain); this interaction serves as bridges to TICAM1 (PubMed:21703541). Component of the B-WICH complex, at least composed of SMARCA5/SNF2H, BAZ1B/WSTF, SF3B1, DEK, MYO1C, ERCC6, MYBBP1A and DDX21. Interacts with C1QBP. Interacts with JUN. Interacts with WDR46. Interacts with MCM3AP (By similarity). Interacts with WDR43 (PubMed:31128943). Present both in nucleolus and nucleoplasm. Interaction with JUN promotes translocation from the nucleolus to the nucleoplasm. Interaction with WDR46 is required for localization to the nucleolus. Colocalizes in the cytosol with DDX1, DHX36 and TICAM1 (PubMed:21703541). The multi-helicase-TICAM1 complex may translocate to the mitochondria upon poly(I:C) RNA ligand stimulation (PubMed:21703541). Highly expressed in liver and testis. Expressed at lower level in brain, lungs, and skeletal muscle. The helicase and foldase activities reside in two separate domains, the helicase in the N-terminus and the foldase in the C-terminus. The 3 X 5 AA repeats seem to be critical for the RNA folding activity. Acetylation by CREBBP/CBP inhibits the helicase activity. Deacetylation by SIRT7 promotes the helicase activity and overcomes R-loop-mediated stalling of RNA polymerases. Belongs to the DEAD box helicase family. DDX21/DDX50 subfamily.