Optimizing RNA interference for application in mammalian cells.
Ontology highlight
ABSTRACT:
SUBMITTER: Medema RH
PROVIDER: S-EPMC1224236 | biostudies-other | 2004 Jun
REPOSITORIES: biostudies-other
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Project description:RNA interference (RNAi) is a powerful tool for sequence-specific gene knockdown in therapeutic and research applications. However, spatiotemporal control of RNAi is required to decrease nonspecific targeting, potential toxicity, and allow targeting of essential genes. Herein we describe a class of de-novo-designed RNA switches that enable sequence-specific regulation of RNAi in mammalian cells. Using cis-repressing RNA elements, we engineer RNA devices that only initiate microRNA biogenesis when binding with cognate trigger RNAs. We demonstrate that this conditional RNAi system, termed Orthogonal RNA Interference induced by Trigger RNA (ORIENTR), provides up to 14-fold increases in artificial miRNA biogenesis upon activation in orthogonal libraries. We show that integration of ORIENTR triggers with dCas13d enhances dynamic range to up to 31-fold. We further demonstrate that ORIENTR can be applied to detect endogenous RNA signals and to conditionally knockdown endogenous genes, thus enabling regulatory possibilities including cell-type-specific RNAi and rewiring of transcriptional networks via RNA profile.
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Project description:Plants and invertebrates protect themselves from viruses through RNA interference (RNAi), yet it remains unknown whether this defense mechanism exists in mammals. Antiviral RNAi involves the processing of viral long double-stranded (ds) RNA molecules into small interfering RNAs (siRNAs) by the ribonuclease (RNAse) III Dicer. These siRNAs are incorporated into effector complex(es) containing members of the Argonaute (Ago) protein family and guide silencing of complementary target viral RNAs. Here, we detect the accumulation of phased Dicer-dependent virus-derived siRNA (viRNAs) and demonstrate their loading into Ago2 after infection of mouse embryonic stem (ES) cells with Encephalomyocarditis virus (EMCV). We further show that the production of these viRNAs is drastically reduced, yet not completely abolished, if ES cells are first induced to differentiate before infection. Finally, we reveal that the mammalian virus Nodamura virus (NoV) encodes for a protein that counteracts such antiviral RNAi in ES cells supporting the existence of an effective RNAi-based immunity in mammals. Infection of wild-type or mutant mouse ES cells and analysis of small RNAs from total extracts or immunoprecipitated components of the RNAi pathway
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Project description:RNA interference (RNAi) is a widely used method for analysis of gene function in tissue culture cells. However, to date there has been no reliable method for testing the specificity of any particular RNAi experiment. The ideal experiment is to rescue the phenotype by expression of the target gene in a form refractory to RNAi. The transgene should be expressed at physiological levels and with its different splice variants. Here, we demonstrate that expression of murine bacterial artificial chromosomes in human cells provides a reliable method to create RNAi-resistant transgenes. This strategy should be applicable to all eukaryotes and should therefore be a standard technology for confirming the specificity of RNAi. We show that this technique can be extended to allow the creation of tagged transgenes, expressed at physiological levels, for the further study of gene function.
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Project description:RNA interference (RNAi) is a conserved antiviral immune defense in eukaryotes, and numerous viruses have been found to encode viral suppressors of RNAi (VSRs) to counteract antiviral RNAi. Alphaviruses are a large group of positive-stranded RNA viruses that maintain their transmission and life cycles in both mosquitoes and mammals. However, there is little knowledge about how alphaviruses antagonize RNAi in both host organisms. In this study, we identified that Semliki Forest virus (SFV) capsid protein can efficiently suppress RNAi in both insect and mammalian cells by sequestrating double-stranded RNA and small interfering RNA. More importantly, when the VSR activity of SFV capsid was inactivated by reverse genetics, the resulting VSR-deficient SFV mutant showed severe replication defects in mammalian cells, which could be rescued by blocking the RNAi pathway. Besides, capsid protein of Sindbis virus also inhibited RNAi in cells. Together, our findings show that SFV uses capsid protein as VSR to antagonize RNAi in infected mammalian cells, and this mechanism is probably used by other alphaviruses, which shed new light on the knowledge of SFV and alphavirus.IMPORTANCE Alphaviruses are a genus of positive-stranded RNA viruses and include numerous important human pathogens, such as Chikungunya virus, Ross River virus, Western equine encephalitis virus, etc., which create the emerging and reemerging public health threat worldwide. RNA interference (RNAi) is one of the most important antiviral mechanisms in plants and insects. Accumulating evidence has provided strong support for the existence of antiviral RNAi in mammals. In response to antiviral RNAi, viruses have evolved to encode viral suppressors of RNAi (VSRs) to antagonize the RNAi pathway. It is unclear whether alphaviruses encode VSRs that can suppress antiviral RNAi during their infection in mammals. In this study, we first uncovered that capsid protein encoded by Semliki Forest virus (SFV), a prototypic alphavirus, had a potent VSR activity that can antagonize antiviral RNAi in the context of SFV infection in mammalian cells, and this mechanism is probably used by other alphaviruses.
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Project description:Plants and invertebrates protect themselves from viruses through RNA interference (RNAi), yet it remains unknown whether this defense mechanism exists in mammals. Antiviral RNAi involves the processing of viral long double-stranded (ds) RNA molecules into small interfering RNAs (siRNAs) by the ribonuclease (RNAse) III Dicer. These siRNAs are incorporated into effector complex(es) containing members of the Argonaute (Ago) protein family and guide silencing of complementary target viral RNAs. Here, we detect the accumulation of phased Dicer-dependent virus-derived siRNA (viRNAs) and demonstrate their loading into Ago2 after infection of mouse embryonic stem (ES) cells with Encephalomyocarditis virus (EMCV). We further show that the production of these viRNAs is drastically reduced, yet not completely abolished, if ES cells are first induced to differentiate before infection. Finally, we reveal that the mammalian virus Nodamura virus (NoV) encodes for a protein that counteracts such antiviral RNAi in ES cells supporting the existence of an effective RNAi-based immunity in mammals.
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