Of interest, HIV-1 infection is known to up regulate the cellular expression of several RNA helicases including DHX9, DDX11, DDX18, DDX21 and DDX24 [39], and a recent mass spectrometry-based proteomic study identified the binding to Rev-RRE-RNA of eight cellular RNA helicases, DDX1, DDX3, DDX5, DHX9 (RHA), DDX17, DDX24, DHX36, and DDX47 [40]. Here, DHX9 is linked to HIV-1 infection.