RNA helicase A interacts with RISC in human cells and functions in RISC loading

Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Molecular Cell (Impact Factor: 14.02). 06/2007; 26(4):523-37. DOI: 10.1016/j.molcel.2007.04.016
Source: PubMed


RNA interference is a conserved pathway of sequence-specific gene silencing that depends on small guide RNAs and the action of proteins assembled in the RNA-induced silencing complex (RISC). Minimally, the action of RISC requires the endonucleolytic slicer activity of Argonaute2 (Ago2) directed to RNA targets whose sequences are complementary to RISC-incorporated small RNA. To identify RISC components in human cells, we developed an affinity-purification strategy to isolate siRNA-programmed RISC. Here we report the identification of RNA helicase A (RHA) as a human RISC-associated factor. We show that RHA interacts in human cells with siRNA, Ago2, TRBP, and Dicer and functions in the RNAi pathway. In RHA-depleted cells, RNAi was reduced as a consequence of decreased intracellular concentration of active RISC assembled with the guide-strand RNA and Ago2. Our results identify RHA as a RISC component and demonstrate that RHA functions in RISC as an siRNA-loading factor.

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    • "The two strands subsequently separate and one strand associates with Argonaute 2 (AGO2), a protein component of the RNAinduced silencing complex (RISC). Unwinding of the duplex to generate the guide strand and the passenger strand is achieved by a combination of helicases associated with the RISC complex (exactly which remains to be determined, although helicases associated with RISC formation and/or activity include p68, p72, RNA helicase A, TNRC6B and Gemin3/4 (Meister et al. 2005, Robb & Rana 2007, Salzman et al. 2007)). The mature miR guides RISC to complementary sequences within the 3 0 -UTR of target mRNAs, resulting in translational repression and/or transcript degradation. "
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    • "RNA helicase A (RHA or DHX9) is a DExH-box helicase, a member of Superfamily (SF) 2. This protein is essential for mammalian embryogenesis (9) and has been shown to participate in diverse cellular functions including transcription (10), translation (11), RNA interference pathway (12) and innate immune response (13). RHA can promote replication of a number of viruses including HIV-1 (14–18). "
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