Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RNAi”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

Expediting target identification and validation through RNAi.

RNA interference (RNAi) is an efficient post-transcriptional gene silencing mechanism that is induced by double-stranded RNA. Applications of RNAi have gained increasing attention since the groundbreaking discovery that small interfering RNA (siRNA) molecules can be used to inhibit gene expression in mammalian cells in a sequence-specific manner. Numerous meetings have recently been held in this field, but the organiser from EF International succeeded in bringing some of the leading academic scientists and company researchers together in London to present and discuss exciting new results. Major topics covered in the meeting included the recent progress in understanding the basic mechanism of RNAi, genome-wide RNAi-based screens for target discovery, and approaches to use RNAi for target validation in cell culture and in animal models. In addition, borders and caveats of the technology, such as off-target effects and a possible induction of the interferon response by siRNA, have been discussed intensively. The use of siRNAs can be regarded as a highly potent strategy to identify and validate new targets for therapeutic interventions against cancer, viral infections, chronic pain and other diseases. Finally, siRNAs themselves hold the promise to become therapeutic agents in the near future.

Animals↗

Intravenous, non-viral RNAi gene therapy of brain cancer.

RNA interference (RNAi) has the potential to knock down oncogenes in cancer, including brain cancer. However, the therapeutic potential of RNAi will not be realised until the rate-limiting step of delivery is solved. The development of RNA-based therapeutics is not practical, due to the instability of RNA in vivo. However, plasmid DNA can be engineered to express short hairpin RNA (shRNA), similar to endogenous microRNAs. Intravenous, non-viral RNAi-based gene therapy is enabled with a new gene-targeting technology, which encapsulates the plasmid DNA inside receptor-specific pegylated immunoliposomes (PILs). The feasibility of this RNAi approach was evaluated by showing it was possible to achieve a 90% knockdown of brain tumour-specific gene expression with a single intravenous injection in adult rats or mice with intracranial brain cancer. The survival of mice with intracranial human brain cancer was extended by nearly 90% with weekly intravenous injections of PILs carrying plasmid DNA expressing a shRNA directed against the human epidermal growth factor receptor. RNAi-based gene therapy can be coupled with gene therapy that replaces mutated tumour suppressor genes to build a polygenic approach to the gene therapy of cancer.

Animals↗

Stable suppression of gene expression in murine embryonic stem cells by RNAi directed from DNA vector-based short hairpin RNA.

Murine embryonic stem (ES) cells are an ideal system for the research of directed differentiation in vitro. Long double-stranded RNA, which can induce RNA interference (RNAi) effectively in many organisms, has been shown to suppress target gene expression efficiently and specifically in undifferentiated ES cells. However, it cannot be used in differentiated ES cells due to unspecific inhibition of gene expression resulting from the activation of interferon pathway following differentiation. Using green fluorescent protein (GFP) as a reporter system, we show here that a short hairpin RNA (shRNA) expression vector driven by the murine U6 small nuclear RNA promoter can specifically induce potent gene knockdown effect (i.e., inhibit GFP expression specifically) when transfected transiently into ES cells. Furthermore, when the expression vector is stably integrated into the genome of the cell, it can still show specific RNAi effect, which can be maintained at least for 10 days. These transfected ES cells showed no obvious differences in the morphology or growth rate in culture compared with untransfected cells, suggesting that the activation of shRNA-directed RNAi did not affect the properties of ES cells and that the RNAi effect in ES cells is specific and persistent. Our results prove the feasibility of the U6 promoter-driven shRNA expression technique to be used to study the function of genes expressed in ES cells. These ES cells, after integration of the U6-based RNAi vector into their genome, could be used to generate gene knockdown mice.

Animals↗

D-RNAi (messenger RNA-antisense DNA interference) as a novel defense system against cancer and viral infections.

D-RNAi (Messenger RNA-antisense DNA interference), a novel posttranscriptional phenomenon of silencing gene expression by transfection of mRNA-aDNA hybrids, was originally observed in the effects of bcl-2 on phorbol ester-induced apoptosis in human prostate cancer LNCaP cells. This phenomenon was also demonstrated in chicken embryos and a human CD4(+) T cell line, H9. The in vivo transduction of beta-catenin D-RNAi was shown to knock out more than 99% endogenous beta-catenin gene expression, while the in cell transfection of HIV-1 D-RNAi homolog rejected viral gene replication completely. D-RNAi was found to have long-term gene knockout effects resulting from a posttranscriptional gene silencing mechanism that may involve the homologous recombination between intracellular mRNA and the mRNA components of a D-RNAi construct. These findings provide a potential intracellular defense system against cancer and viral infections.

DNA, Antisense↗

RNAi in functional genomics.

There has been a lack of powerful tools for systematic analysis of mammalian gene function, but RNA interference (RNAi) may now provide such a strategy. Stable transcription of RNAi triggers from suitable expression cassettes integrated into the host cell genome by viral gene transfer can induce long-term and heritable gene silencing in mammalian cells. However, the use of RNAi as a genetic tool is limited by difficulties in identifying efficient RNAi triggers, the problem of effective delivery and off-target effects, as well as potential genotoxic side effects of viral gene transfer strategies. Recent insights into the molecular mechanisms of silencing processes mediated by either siRNA or miRNA will allow further optimization of RNAi triggers as genetic tools.

Animals↗

[Application of RNAi technology to knockdown gene expression in vivo in mammalians].

Post-transcriptional gene silencing (PTGS) initiated by dsRNA, which result in specific degradation of homologous mRNA, is called RNAi. The discovery of RNAi greatly intrigued researchers, and was followed by a flood of papers that described the phenomenon and mechanism of RNAi. More excitingly, RNAi has recently been developed into a new tool, showing promising role in reverse genetics, gene therapy and anti-viral infection. This review provides the progress of the application of RNAi technology in mammalian animals.

Animals↗

RNAi versus small molecules: different mechanisms and specificities can lead to different outcomes.

The methodology of RNA interference (RNAi) arrived on the scene of mammalian systems research in 2001. Since that time, there has been widespread use of this technology in both academic and industrial settings. RNAi and small molecules were initially considered as equivalent methods for inhibiting protein activity within cells, but as our understanding of the mechanism of RNAi has improved, it has become apparent that differences in their cellular mechanisms have unexpected consequences. There can be profound differences in the phenotypic outcomes of treatment with RNAi versus small molecules. This review discusses the similarities, as well as the predicted differences between RNAi and small molecule effects on therapeutic paradigms and drug discovery.

Animals↗

[The application of RNAi technology in transgenic mice].

RNA interference (RNAi) has been extensively used for sequence-specific silencing of gene function in C. elegans, Drosophila, mouse and rat. The generation of RNAi transgenic mice made it possible to knock down gene expression at the whole organism level in mammalian species. In this review we described the design strategy of RNAi vectors, compared the difference of gene knock-down from knock-out, and summarized the advantages and unresolved issues concerning RNAi transgenic mice. The contribution of RNAi transgenic mice to functional genomics and of its prospect for application were also discussed.

Animals↗

[Effects of hTERT RNAi on apoptosis of hepatocellular carcinoma cells induced by TRAIL].

OBJECTIVE: To study the effects of human telomerase reverse transcriptase (hTERT) RNA interference (RNAi) on biological characteristics of hepatocellular carcinoma cell lines HepG2 and SMMC-7721 and on apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). METHODS: Small hairpin hTERT (shTERT) sequence was identified by PCR method; hTERT expressions, morphological features, cell proliferation and replicative senescence were respectively determined using RT-PCR, hematoxylin-eosin (HE) staining, growth curve and beta-galactosidase (b-Gal) staining; cell cycle and apoptosis were identified using flow cytometry after propidium iodide (PI) staining and annexin V/PI double staining. RESULTS: shRNA were found in 6/8 HepG2 and 6/6 SMMC-7721 cell clones transformed by the recombined plasmid pSilencer 3.1-H1 neo-shTERT. The interference rates of hTERT on HepG2 and SMMC-7721 were 100% and 43.3% respectively. Cells in G2-M phases increased from 7.1% to 10.6% and from 6.9% to 7.9% respectively; and the percentage of replicative senenscence cells increased from 0 to 20.4% and from 3.6% to 10.0% respectively. The nucleus/cytoplasm ratios of the cells were obviously decreased after hTERT RNAi treatment. Moreover, apoptosis of hepatocellular carcinoma cells and apoptosis induced by TRAIL were strikingly increased by hTERT RNAi (P < 0.05). For example, apoptosis rates were increased from 3.5% to 5.2% in HepG2 cells and from 4.8% to 7.9% in SMMC-7721 cells after hTERT RNAi treatment. Apoptosis rates were increased from 5.3% to 10.4% in HepG 2 cells and from 13.9% to 77.2% in SMMC-7721 cells after being treated by 100 ng/ml TRAIL for 24 h. However, there were no remarkable changes between control cells and untransformed cells. CONCLUSION: hTERT RNAi not only has a significant effect on biological characteristics of hepatocellular carcinoma cells, but also obviously can increase cell apoptosis induced by TRAIL.

Apoptosis↗

The effect of an immune RNA (RNAi) against Trypanosoma cruzi infection in mice.

Immune ribonucleic acid (RNAi) was extracted with phenol from the spleen of mice immunized with the avirulent PF strain of Trypanosoma cruzi. These preparations were able to induce immunocompetent cells to answer as a secondary response to later challenges with the virulent Y strain of the same parasite. The preparations of RNAi were"immunogenic" and free of proteins. The RNAi preparations were sensitive to pancreatic RNAase and lost their immune effect when pretreated with this enzyme. The injections of normal RNA (RNAn) obtained by the same method showed that this polymer acts as an immuno supressor or competitive agent. The electrophoretic profiles of the RNAi preparations in polyacrylamide gels showed normal and characteristic migration patterns (28S, 18S and 4.5S). These results demonstrate the development of an immune state against T. cruzi infection in mice injected with RNAi, in the absence of living parasites.

Animals↗

Screening, optimization and artificial recombination of dsRNA fragments for RNAi-mediated pest resistance in Apolygus lucorum.

RNA interference (RNAi) is an eco-friendly strategy for pest management, with double-stranded RNA (dsRNA) as the core functional component. In this study, three RNAi target genes (Ubx, wupA and Dpp) with strong lethal effects on Apolygus lucorum were screened via microinjection. The 7-day cumulative mortalities were 56.67 &#xb1; 3.33% for dsUbx, 94.44 &#xb1; 1.11% for dswupA and 92.22 &#xb1; 1.11% for dsDpp. We optimized dsRNA sequences by removing conserved sequences in non-target organisms based on homology alignment and off-target risk analysis. The optimized fragments dswupA-OTE and dsDpp-OTE still exhibited high insecticidal activity, with 7-day cumulative mortalities of 77.78 &#xb1; 2.94% and 70.00 &#xb1; 1.93%, respectively. We also evaluated the effects of dsRNA length and target sites on RNAi efficiency and screened potent short dsRNA fragments. Novel artificially recombinant dsRNAs were constructed by assembling effective short fragments from different genes, which retained strong insecticidal activity despite shorter sequence length. This study verifies the feasibility of multi-target recombinant dsRNA for pest control and provides a theoretical basis for developing multi-gene RNAi technologies against A. lucorum.

Apolygus lucorum↗

RNAi and microRNAs: from animal models to disease therapy.

The discovery of the phenomenon of RNA interference (RNAi) and its existence in mammals quickly suggested a great potential for use in disease therapy. Rapid advances have been made in the development of RNAi-based technologies and promising results have been obtained from studies on mammalian cell culture systems and animal in vivo models. However, the progress in our understanding of the RNAi pathway and the related function of microRNAs (miRNAs) have also raised concerns regarding various types of side effects that may restrict the use of this technology in human therapy. At the same time, our new knowledge about the functional roles of miRNAs as regulators of many cellular processes, including proliferation, differentiation, development, and neuronal function, is revolutionizing cell biology and will have a major impact on medical research. In this review, we focus on the discoveries that have been made in animal models and how this insight can be translated to human medicine and disease therapy. In this connection, we will particularly discuss the challenges associated with the efforts to develop RNAi-based therapeutics.

Animals↗

RNAi knockdown of the focal adhesion protein TES reveals its role in actin stress fibre organisation.

TES was originally identified as a candidate tumour suppressor gene and has subsequently been found to encode a novel focal adhesion protein. As well as localising to cell-matrix adhesions, TES localises to cell-cell contacts and to actin stress fibres. TES interacts with a variety of cytoskeletal proteins including zyxin, mena, VASP, talin and actin. There is evidence that TES may function in actin-dependent processes as overexpression of TES results in increased cell spreading and decreased cell motility. Together with TES's interacting partners, these data suggest that TES might be involved in regulation of the actin cytoskeleton. Here, for the first time, we have used RNAi to successfully knockdown TES in HeLa cells and we demonstrate that loss of TES from focal adhesions results in loss of actin stress fibres. Similarly, and as previously reported, RNAi-mediated knockdown of zyxin results in loss of actin stress fibres. TES siRNA treated cells show reduced RhoA activity, suggesting that the Rho GTPase pathway may be involved in the TES RNAi-induced loss of stress fibres. We have also used RNAi to examine the requirement of TES and zyxin for each other's localisation at focal adhesions, and we propose a hierarchy of recruitment, with zyxin being first, followed by VASP and then TES. Cell Motil.

Actins↗

In vivo comparative study of RNAi methodologies by in ovo electroporation in the chick embryo.

The combination of emergent RNA interference (RNAi) technology with in ovo electroporation in the chick embryo has the potential to provide a powerful and rapid means for functional analyses of novel genes in vivo. In this study, we show that electroporation of short 21-bp RNA duplexes (siRNAs) is a quick and simple method for silencing exogenous and endogenous gene expression in vivo. Quantitative comparisons with two other RNAi protocols that use long double-stranded RNA duplexes and endonuclease-digested duplexes (esiRNAs) demonstrate that siRNAs are significantly more effective at reducing gene expression. Furthermore, we also find that much higher amounts of siRNA are required for silencing of endogenous gene expression relative to plasmid-borne reporter constructs. In short, these results demonstrate that siRNAs are the most effective type of double-stranded RNA duplex for silencing gene expression and suggest that there might be important differences between silencing endogenous and exogenous genes. Finally, we review the parameters for each of these RNA-based methods of RNAi and the controls required to analyze RNAi data in the context of the developing vertebrate embryo.

Animals↗

RNAi-mediated inhibition of gene function in the follicle cell layer of the Drosophila ovary.

RNA-mediated interference (RNAi) has been reported to be an effective reverse genetic approach for studying gene function in various organisms. To assess RNAi as a means of examining genes expressed in ovarian follicle cells for their involvement in embryonic dorsal-ventral patterning, we tested the ability of transgenically expressed double-stranded RNA (dsRNA) directed against the dorsal group gene windbeutel to generate phenotypic effects in the progeny of expressing females. We observed that expression in follicle cells under the control of Gal4 transcribed from the strong and widely expressed alphaTub84B or Actin5C promoters led to efficient dorsalization of progeny embryos. Surprisingly, a variety of strongly expressed follicle cell-specific Gal4 enhancer trap lines failed to elicit an RNAi phenotype in combination with the windbeutel-specific dsRNA. These results stress the importance of careful choice of expression system and of conditions for use in transgenic RNAi-mediated studies of gene function.

Animals↗

RNAi-based suppression and replacement of rds-peripherin in retinal organotypic culture.

Extensive mutational heterogeneity presents a significant barrier to the development of therapeutics for RDS-peripherin-linked autosomal-dominant retinitis pigmentosa (RP), for which more than 50 disease-related mutations have been identified to date. Mutation-independent suppression, using RNA interference (RNAi), together with simultaneous expression of a replacement rds gene (r-rds, which has been altered to escape suppression but nevertheless encodes wild-type protein) has been explored in COS-7 cells and mouse retinal explants. The efficacy of small interfering and short hairpin RNAs (si/shRNAs) silencing mouse rds, and the function of r-rds (containing degenerate substitutions in the RNAi target sequence) were analyzed at transcript (RT-PCR) and protein (ELISA) levels in COS-7 cells. "Dual-" and "triple-expression" constructs carrying the shRNA suppressor and the marker EGFP with or without the r-rds cassette were electroporated in vitro into retinal explants from 1-day-old pups. The retinae were dissociated at day 14, and transduced cells were FACS-sorted using the coexpressed EGFP marker and analyzed by RT-PCR. si/shRNAs decreased rds mRNA and protein expression by up to 82%, while r-rds was protected from suppression in COS-7 cells. Similarly, efficient RNAi-mediated suppression of endogenous rds was detected in retinal explants, while concomitant rescue of r-rds was also achieved. These data validate the concept of RNAi-based suppression coupled with replacement technology for the development of therapies targeting RDS-linked autosomal-dominant RP, and suggest that such approaches could potentially be used for other autosomal-dominant diseases with similarly extensive intragenic heterogeneity.

Animals↗

Adenovirus VA RNAI mediates a translational stimulation which is not restricted to the viral mRNAs.

The effect of adenovirus VA RNAI on the translation of mRNAs expressing the bacterial chloramphenicol acetyltransferase (CAT) enzyme was studied by a transient expression assay in 293 cells. The CAT activity was determined in extracts prepared from cells transfected with mixtures of plasmids encoding CAT and VA RNA. The results showed that VA RNAI co-transfection resulted in a significant increase in CAT expression from a variety of constructs. Thus, expression of CAT from a SV40 mRNA, a beta-globin mRNA and a chimeric mRNA containing the adenovirus-2 tripartite leader were all stimulated approximately 6-fold by VA RNAI. Based on these results we conclude that the tripartite leader sequence is not required for the VA RNA-mediated stimulation of translation. Our results indicate instead that VA RNAI probably functions as a general enhancer of mRNA translation. A2- to 3-fold stimulation of CAT expression was also obtained following transient expression of HeLa and CV-1 cells. The reduced efficiency was correlated with a 10- to 20-fold lower level of VA RNA expression in HeLa compared with 293 cells. Thus, it is likely that a product from region E1 indirectly enhances the translational efficiency by stimulating VA RNA transcription.

Acetyltransferases↗

Effects of mutations in stem and loop regions on the structure and function of adenovirus VA RNAI.

Adenovirus virus-associated (VA) RNAI is required for efficient protein synthesis at late times of adenoviral infection, and in some other situations where double-stranded RNA (dsRNA) is present. It prevents inhibition of protein synthesis by a dsRNA-activated protein kinase and the secondary structure of VA RNAI is though to be important for its activity. To test this idea and to define structures and sequences responsible for VA RNAI activity, we constructed several mutant VA RNA genes and tested them in a transient expression assay. Activity is unaffected by deletions within a small region near the center of the gene, nt 72-85, but it is greatly diminished by deletion or substitution of sequences on the 3' side of this region. The structures of wild-type and mutant RNAs were examined by nuclease-sensitivity analysis. We propose a model for wild-type VA RNAI which differs from that predicted to be the most stable structure. Surprisingly disruption of the longest duplex region in the molecule is tolerated, provided that adjacent structural elements are not rearranged. However, perturbations of elements located in the center of the structure correlate well with loss of function.

Adenoviruses, Human↗