HIV-1 RRE RNA acts as an RNA silencing suppressor by competing with TRBP-bound siRNAs

Abstract

Several proteins and RNAs expressed by mammalian viruses have been reported to interfere with RNA interference (RNAi) activity. We investigated the ability of the HIV-1-encoded RNA elements Trans-Activation Response (TAR) and RevResponse Element (RRE) to alter RNAi. MicroRNA let7-based assays showed that RRE is a potent suppressor of RNAi activity, while TAR displayed moderate RNAi suppression. We demonstrate that RRE binds to TAR-RNA Binding Protein (TRBP), an essential component of the RNA Induced Silencing Complex (RISC). The binding of TAR and RRE to TRBP displaces small interfering (si)RNAs from binding to TRBP. Several stem-deleted RRE mutants lost their ability to suppress RNAi activity, which correlated with a reduced ability to compete with siRNA-TRBP binding. A lentiviral vector expressing TAR and RRE restricted RNAi, but RNAi was restored when Rev or GagPol were coexpressed. Adenoviruses are restricted by RNAi and encode their own suppressors of RNAi, the Virus-Associated (VA) RNA elements. RRE enhanced the replication of wild-type and VA-deficient adenovirus. Our work describes RRE as a novel suppressor of RNAi that acts by competing with siRNAs rather than by disrupting the RISC. This function is masked in lentiviral vectors co-expressed with viral proteins and thus will not affect their use in gene therapy. The potent RNAi suppressive effects of RRE identified in this study could be used to enhance the expression of RNAi restricted viruses used in oncolysis such as adenoviruses.

ADAR1 and PACT contribute to efficient translation of transcripts containing HIV-1 trans-activating response (TAR) element

“…To determine if PACT can enhance HIV-1 long terminal repeat (LTR)-driven gene expression in the context of latently infected cells, we first compared the effects of TRBP and PACT when HIV-1 LTR is integrated into the host chromosome. HeLa-MAGI-CCR5 cells contain a stably integrated β-galactosidase-coding region expressed under the control of the HIV-1 LTR, whose transcription is dependent on HIV-1 Tat protein [45][46][47][48][49]. We first verified that increasing amounts of Tat expression vector (blue bars) resulted in a dose-dependent increase in β-galactosidase activity ( Figure 1A) compared with the absence of Tat (black bar).…”

The Diverse Roles of microRNAs at the Host–Virus Interface

“…Therefore, it is possible that Tat binds to specific precursor miRNAs in a sequence-dependent manner, inhibiting Dicer processing of this subset of miRNAs. Additionally, a structured RNA element of the HIV-1 genome, the Rev-response element (RRE), binds to the TRBP, a central component of the Dicer complex [ 176 , 177 , 178 ]. This interaction further inhibits the RNA silencing pathway by competing with TRBP-bound RNAs [ 177 ].…”

“…Additionally, a structured RNA element of the HIV-1 genome, the Rev-response element (RRE), binds to the TRBP, a central component of the Dicer complex [ 176 , 177 , 178 ]. This interaction further inhibits the RNA silencing pathway by competing with TRBP-bound RNAs [ 177 ]. Similarly to HIV-1, the primate foamy virus type 1 (PFV-1) encoded transactivator (Tas) also interferes with miRNA processing, and might function to overcome suppression of PFV-1 replication mediated by the cellular miRNA, miR-32 [ 179 ].…”

ROLE OF COMPONENTS OF microRNA MACHINERY IN CARCINOGENESIS

“…The active strand of such mature miRNA is retained in the Dicer-TRBP complex, which then binds with the endonuclease AGO2. One strand of the mature miRNA (the guide strand) is loaded into the RISC target mRNAs that are complementary to the miRNA [84]. Huang et al [85] revealed that TRBP is overexpressed in BC.…”