DDX3X belongs to the DEAD (Asp-Glu-Ala-Asp)-box protein family of RNA helicases, involved in the alteration of RNA secondary structure required for transcription, mRNA processing, and translation initiation. DDX3X is an essential host factor during virus infection. DDX3X serves as the cellular target of Hepatitis C virus (HCV) core protein, and also facilitates nuclear export of immature HIV RNA. The RNA helicase activity of DDX3X is required for the replication of both HCV and HIV. DDX3X is implied to act as a viral RNA sensor, mediating antiviral innate immune signaling. DDX3 participates in IκB kinase ε (IKKε) and TANK-binding kinase 1 (TBK1) dependent IRF3 activation, leading to the production of Type I interferon. DDX3X was also proposed to have antiapoptotic functions and participate in tumorigenesis.