Multifunctional ATP-dependent RNA helicase (PubMed:17357160, PubMed:21589879, PubMed:31575075). The ATPase activity can be stimulated by various ribo-and deoxynucleic acids indicative for a relaxed substrate specificity (PubMed:29222110). In vitro can unwind partially double-stranded DNA with a preference for 5'-single-stranded DNA overhangs (PubMed:17357160, PubMed:21589879). Binds RNA G-quadruplex (rG4s) structures, including those located in the 5'-UTR of NRAS mRNA (PubMed:30256975). Involved in many cellular processes, which do not necessarily require its ATPase/helicase catalytic activities (Probable). Involved in transcription regulation (PubMed:16818630, PubMed:18264132). Positively regulates CDKN1A/WAF1/CIP1 transcription in an SP1-dependent manner, hence inhibits cell growth. This function requires its ATPase, but not helicase activity (PubMed:16818630, PubMed:18264132). CDKN1A up-regulation may be cell-type specific (PubMed:18264132). Binds CDH1/E-cadherin promoter and represses its transcription (PubMed:18264132). Potentiates HNF4A-mediated MTTP transcriptional activation; this function requires ATPase, but not helicase activity. Facilitates HNF4A acetylation, possibly catalyzed by CREBBP/EP300, thereby increasing the DNA-binding affinity of HNF4 to its response element. In addition, disrupts the interaction between HNF4 and SHP that forms inactive heterodimers and enhances the formation of active HNF4 homodimers. By promoting HNF4A-induced MTTP expression, may play a role in lipid homeostasis (PubMed:28128295). May positively regulate TP53 transcription (PubMed:28842590). Associates with mRNPs, predominantly with spliced mRNAs carrying an exon junction complex (EJC) (PubMed:17095540, PubMed:18596238). Involved in the regulation of translation initiation (PubMed:18628297, PubMed:17667941, PubMed:22872150). Not involved in the general process of translation, but promotes efficient translation of selected complex mRNAs, containing highly structured 5'-untranslated regions (UTR) (PubMed:20837705, PubMed:22872150). This function depends on helicase activity (PubMed:20837705, PubMed:22872150). Might facilitate translation by resolving secondary structures of 5'-UTRs during ribosome scanning (PubMed:20837705). Alternatively, may act prior to 43S ribosomal scanning and promote 43S pre-initiation complex entry to mRNAs exhibiting specific RNA motifs, by performing local remodeling of transcript structures located close to the cap moiety (PubMed:22872150). Independently of its ATPase activity, promotes the assembly of functional 80S ribosomes and disassembles from ribosomes prior to the translation elongation process (PubMed:22323517). Positively regulates the translation of cyclin E1/CCNE1 mRNA and consequently promotes G1/S-phase transition during the cell cycle (PubMed:20837705). May activate TP53 translation (PubMed:28842590). Required for endoplasmic reticulum stress-induced ATF4 mRNA translation (PubMed:29062139). Independently of its ATPase/helicase activity, enhances IRES-mediated translation; this activity requires interaction with EIF4E (PubMed:17667941, PubMed:22323517). Independently of its ATPase/helicase activity, has also been shown specifically repress cap-dependent translation, possibly by acting on translation initiation factor EIF4E (PubMed:17667941). Involved in innate immunity, acting as a viral RNA sensor. Binds viral RNAs and promotes the production of type I interferon (IFN-alpha and IFN-beta) (PubMed:31575075, PubMed:20127681, PubMed:21170385). Potentiate MAVS/DDX58-mediated induction of IFNB in early stages of infection (PubMed:20127681, PubMed:21170385). Enhances IFNB1 expression via IRF3/IRF7 pathway and participates in NFKB activation in the presence of MAVS and TBK1 (PubMed:18583960, PubMed:18636090, PubMed:21170385, PubMed:27980081, PubMed:19913487). Involved in TBK1 and IKBKE-dependent IRF3 activation leading to IFNB induction, acts as a scaffolding adapter that links IKBKE and IRF3 and coordinates their activation (PubMed:23478265). Involved in the TLR7/TLR8 signaling pathway leading to type I interferon induction, including IFNA4 production. In this context, acts as an upstream regulator of IRF7 activation by MAP3K14/NIK and CHUK/IKKA. Stimulates CHUK autophosphorylation and activation following physiological activation of the TLR7 and TLR8 pathways, leading to MAP3K14/CHUK-mediated activatory phosphorylation of IRF7 (PubMed:30341167). Also stimulates MAP3K14/CHUK-dependent NF-kappa-B signaling (PubMed:30341167). Negatively regulates TNF-induced IL6 and IL8 expression, via the NF-kappa-B pathway. May act by interacting with RELA/p65 and trapping it in the cytoplasm (PubMed:27736973). May also bind IFNB promoter; the function is independent of IRF3 (PubMed:18583960). Involved in both stress and inflammatory responses (By similarity). Independently of its ATPase/helicase activity, required for efficient stress granule assembly through its interaction with EIF4E, hence promotes survival in stressed cells (PubMed:21883093). Independently of its helicase activity, regulates NLRP3 inflammasome assembly through interaction with NLRP3 and hence promotes cell death by pyroptosis during inflammation. This function is independent of helicase activity (By similarity). Therefore DDX3X availability may be used to interpret stress signals and choose between pro-survival stress granules and pyroptotic NLRP3 inflammasomes and serve as a live-or-die checkpoint in stressed cells (By similarity). In association with GSK3A/B, negatively regulates extrinsic apoptotic signaling pathway via death domain receptors, including TNFRSF10B, slowing down the rate of CASP3 activation following death receptor stimulation (PubMed:18846110). Cleavage by caspases may inactivate DDX3X and relieve the inhibition (PubMed:18846110). Independently of its ATPase/helicase activity, allosteric activator of CSNK1E. Stimulates CSNK1E-mediated phosphorylation of DVL2, thereby involved in the positive regulation of Wnt/beta-catenin signaling pathway. Also activates CSNK1A1 and CSNK1D in vitro, but it is uncertain if these targets are physiologically relevant (PubMed:23413191, PubMed:29222110). ATPase and casein kinase-activating functions are mutually exclusive (PubMed:29222110). May be involved in mitotic chromosome segregation (PubMed:21730191). (Microbial infection) Facilitates hepatitis C virus (HCV) replication (PubMed:29899501). During infection, HCV core protein inhibits the interaction between MAVS and DDX3X and therefore impairs MAVS-dependent INFB induction and might recruit DDX3X to HCV replication complex (PubMed:21170385). (Microbial infection) Facilitates HIV-1 replication (PubMed:15507209, PubMed:18583960, PubMed:21589879, PubMed:22872150, PubMed:29899501). Acts as a cofactor for XPO1-mediated nuclear export of HIV-1 Rev RNAs (PubMed:15507209, PubMed:18583960, PubMed:29899501). This function is strongly stimulated in the presence of TBK1 and requires DDX3X ATPase activity (PubMed:18583960). (Microbial infection) Facilitates Zika virus (ZIKV) replication. (Microbial infection) Facilitates Dengue virus (DENV) replication. (Microbial infection) Facilitates Venezuelan equine encephalitis virus (VEEV) replication. ATP + H2O = ADP + H(+) + phosphate kcat is 14 min(-1) for ATP hydrolysis in the absence of nucleic acid (PubMed:17357160). kcat is 36 min(-1) for ATP hydrolysis in the presence of ssDNA oligonucleoside dA200 (PubMed:17357160). kcat is 1.6 min(-1) for ATP hydrolysis in the absence of nucleic acid (PubMed:21589879). kcat is 3.2 min(-1) for ATP hydrolysis in the presence of RNA oligo(rU)20 (PubMed:21589879). kcat is 3.8 min(-1) for ATP hydrolysis in the presence of DNA oligo(dT)20 (PubMed:21589879). Homodimer; can bind RNA as a monomer and as a dimer/oligomer (PubMed:27546789, PubMed:31300642). Interacts with TDRD3 (PubMed:18632687). Interacts (when phosphorylated at Ser-102) with IRF3; the interaction facilitates the phosphorylation and activation of IRF3 by IKBKE (PubMed:23478265, PubMed:27980081). Directly interacts with XPO1/CRM1 (PubMed:15507209, PubMed:30131165, PubMed:31575075). The interaction with XPO1/CMR1 is dependent on the DDX3X nuclear export signal motif and XPO1 interaction with GTPase RAN in its active GTP-bound form (PubMed:31575075, PubMed:30131165). Weakly interacts with TBKBP1/SINTBAD (PubMed:27980081). Directly interacts with TRAF3; this interaction stimulates TRAF3 'Lys-63' ubiquitination (PubMed:27980081). Interacts with CSNK1E in a Wnt-dependent manner; this interaction greatly enhances CSNK1E affinity for ATP, stimulates its kinase activity and promotes CSNK1E-mediated DVL2 phosphorylation (PubMed:23413191, PubMed:29222110). In the presence of RNA, the interaction is decreased (PubMed:29222110). Also interacts with CSNK1D and stimulates its kinase activity (PubMed:23413191, PubMed:29222110). Interacts with TRPV4; this interaction is decreased when the TRPV4 channel is activated, leading to DDX3X relocalization to the nucleus (PubMed:29899501). Interacts with MAP3K14/NIK (PubMed:30341167). Directly interacts with CHUK/IKKA after physiological activation of the TLR7 and TLR8 pathways; this interaction enhances CHUK autophosphorylation (PubMed:30341167). May associate with EIF4F complex, composed of at least EIF4A, EIF4E and EIF4G1/EIF4G3 (Probable). Directly interacts with EIF4E in an RNA-independent manner; this interaction enhances EIF4E cap-binding ability (PubMed:17667941, PubMed:21883093, PubMed:28733330). Directly interacts with EIF4G1 in an RNA-independent manner (PubMed:22872150). DDX3X competes with EIF4G1 for interaction with EIF4E (PubMed:17667941, PubMed:21883093). Interacts with EIF4A1 and EIF2S1 in an RNA-independent manner (PubMed:18596238, PubMed:22323517). Associates with the eukaryotic translation initiation factor 3 (eIF-3) complex, including with EIF3B and EIF3C subunits (PubMed:18628297, PubMed:22323517). Directly interacts with IKBKE/IKKE; this interaction stimulates IKBKE activating autophosphorylation and is induced upon viral infection (PubMed:18636090, PubMed:20657822, PubMed:23478265, PubMed:27980081). Interacts with TBK1 (PubMed:20375222). Interacts with SP1; this interaction potentiates SP1-induced CDKN1A/WAF1/CIP1 transcription (PubMed:16818630). Interacts with GSK3A and GSK3B (PubMed:18846110). Interacts with several death receptors, inclusing FAS, TNFRSF10A and TNFRSF10B (PubMed:18846110). Recruited to TNFRSF10B in the absence of receptor stimulation. When TNFRSF10B is stimulated, further recruited to the receptor and cleaved by caspases. A large proteolytic fragment remains associated with TNFRSF10B (PubMed:18846110). Interacts (via C-terminus) with NXF1/TAP; this interaction may be partly involved in DDX3X nuclear export and in NXF1 localization to stress granules (PubMed:18596238). Identified in an mRNP complex, composed of at least DHX9, DDX3X, ELAVL1, HNRNPU, IGF2BP1/2, ILF3, PABPC1, PCBP2, PTBP2, STAU1, STAU2, SYNCRIP and YBX1 (PubMed:19029303). The interaction with IGF2BP1/2 is RNA-dependent (PubMed:22323517). Directly interacts with PABPC1/PABP1 in an RNA-independent manner (PubMed:18596238, PubMed:21883093, PubMed:22872150, PubMed:28733330). This interaction increases in stressed cells and decreases during cell recovery (PubMed:21883093). Interacts (via C-terminus) with MAVS/IPS-1; this interaction occurs rapidly, but transiently after Sendai virus infection (PubMed:20127681, PubMed:21170385, PubMed:27980081). The interaction potentiates MAVS-mediated IFNB induction (PubMed:20127681, PubMed:21170385). Interacts with ERCC6/CBS (PubMed:26030138). Interacts with DHX33 in an RNA-independent manner (PubMed:26100019). Interacts with DDX5 in the cytoplasm; this interaction may be more efficient when both proteins are unphosphorylated (PubMed:22034099). Interacts with DDX58/RIG-1 (PubMed:20127681). Interacts with IFIH1/MDA5 (PubMed:20127681). Interacts with NCAPH; this interaction may be important for the NCAPH localization at condensing chromosomes during mitosis (PubMed:21730191). Interacts with NLRP3 (via NACHT domain) under inflammasome-activating conditions (By similarity). Interacts with CAPRIN1 (PubMed:28733330). Interacts with HNF4A and NR0B2/SHP in an RNA-independent manner; this interaction disrupts the interaction between HNF4 and NR0B2 that forms inactive heterodimers and enhances the formation of active HNF4 homodimers (PubMed:28128295). Interacts with CREBBP/CBP (PubMed:28128295). Interacts with EP300/p300 (PubMed:28128295). Interacts with gamma-tubulin (PubMed:28842590). Interacts with phosphorylated TP53 (PubMed:28842590). Directly interacts with RELA/p65; this interaction may trap RELA in the cytoplasm, impairing nuclear relocalization upon TNF activating signals (PubMed:27736973). (Microbial infection) Interacts with hepatitis B virus (HBV) polymerase in the cytoplasm; this interaction may inhibit DDX3X interaction with the IKBKE/TBK1 complex, and hence impair IKBKE/TBK1-mediated increase in IFNB production. (Microbial infection) Directly interacts with hepatitis C virus (HCV) core protein in the cytoplasm. (Microbial infection) Interacts with vaccinia virus (VACV) protein K7. (Microbial infection) Interacts with HIV-1 protein Rev. (Microbial infection) Interacts with Venezuelan equine encephalitis virus non-structural protein 3. Shuttles between the nucleus and the cytosol (PubMed:15507209, PubMed:18636090, PubMed:29899501, PubMed:31575075, PubMed:30131165). Exported from the nucleus partly through the XPO1/CRM1 system and partly through NXF1/TAP (PubMed:15507209, PubMed:18636090, PubMed:18596238, PubMed:31575075, PubMed:30131165). Localizes to nuclear pores on the outer side of the nuclear membrane (PubMed:15507209). In the cytosol, partly colocalizes with mitochondria (PubMed:20127681). At G0, predominantly located in nucleus. In G1/S phase, predominantly cytoplasmic (PubMed:22034099). During prophase/prometaphase, localizes in close proximity to the condensing chromosomes (PubMed:30131165, PubMed:21730191). During telophase, localizes around the newly synthesized nuclear membrane and in the cytoplasm (PubMed:22034099). Colocalizes with TRPV4 at the plasma membrane. When TRPV4 channel is activated, intracellular Ca(2+) levels increase and the calmodulin/CAMKII pathway is activated, relocalizes to the nucleus (PubMed:29899501). WNT3A stimulation promotes DDX3 recruitment to the plasma membrane (PubMed:23413191). At the leading edge of migrating fibroblasts, colocalizes with CAPRIN1 and PABPC1 (PubMed:28733330). Localizes to centrosome throughout the cell cycle and associates with TP53 at centrosome during mitosis (PubMed:28842590). Translocates to the nucleus in response to HPIV-3 virus-mediated infection (PubMed:31575075). Widely expressed (PubMed:15294876). In testis, expressed in spermatids (PubMed:15294876). Expressed in epidermis and liver (at protein level) (PubMed:16818630, PubMed:16301996). The C-terminus (residues 536-662) is dispensable for DDX3X trafficking. Phosphorylated by TBK1; the phosphorylation is required for the synergistic induction of IFNB mediated by TBK1 and DDX3X (PubMed:18583960). Phosphorylated by IKBKE at Ser-102 after ssRNA viral infection; enhances the induction of INFB promoter by IRF3 (PubMed:18583960, PubMed:23478265). The cytoplasmic form is highly phosphorylated in the G1/S phase of the cell cycle and much less at G2/M (PubMed:22034099). Phosphorylation by CSNK1E may inhibit RNA-stimulated ATPase activity (PubMed:29222110). Upon stimulation of death receptors, including TNFRSF10B, recruited to receptors and cleaved by caspases. Proteolytic fragments remain associated with the receptors. This cleavage presumably inactivates DDX3X anti-apoptotic function. The disease is caused by variants affecting the gene represented in this entry. Encoded by an chromosome X-linked gene which may escape X chromosome inactivation in females. DDX3Y, its homolog on chromosome Y, is located on the Y non-recombinant portion. Belongs to the DEAD box helicase family. DDX3/DED1 subfamily. The role of the nuclear export signal (NES) motif in XPO1-mediated DDX3X export is controversial (PubMed:30131165, PubMed:31575075, PubMed:15507209). In one study, NES has been found dispensable for DDX3X export while the helicase domain mediates the interaction with XPO1 (PubMed:15507209). However, in two other studies, DDX3X nuclear export is dependent on both NES and Ran in its GTP-bound form while the helicase domain is not required (PubMed:30131165, PubMed:31575075).