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At least 397 records · Page 22Linked to original sources
PubMed2003

Comparative analysis of DNA vectors at mediating RNAi in Anopheles mosquito cells and larvae.

Heritable RNA interference (RNAi) mediated by transgenes exhibiting dyad symmetry represents an important tool to study the function of genes expressed at late developmental stages. In this study, we determined whether the transcriptional machinery of Anopheles mosquitoes is capable of directing suppression of gene expression from DNA constructs designed to transcribe double-stranded RNA (dsRNA) as extended hairpin-loop RNAs. A series of DNA vectors containing sense and antisense regions of the green fluorescent protein EGFP target gene was developed. The effect of these vectors on a transiently expressed or stably integrated EGFP gene was assessed in an Anopheles gambiae cell line and in Anopheles stephensi larvae. Our data indicate that dsRNA-mediated silencing of a target gene from plasmid DNA can be achieved at high levels in Anopheles cell lines and larvae. The region that links the sense and antisense sequences of the target gene plays a determining role in the degree of silencing observed. These results provide important information for the development of heritable RNAi in Anopheles.

Animals↗
PubMed2003

Lentivirus-delivered stable gene silencing by RNAi in primary cells.

Genome-wide genetic approaches have proven useful for examining pathways of biological significance in model organisms such as Saccharomyces cerevisiae, Drosophila melanogastor, and Caenorhabditis elegans, but similar techniques have proven difficult to apply to mammalian systems. Although manipulation of the murine genome has led to identification of genes and their function, this approach is laborious, expensive, and often leads to lethal phenotypes. RNA interference (RNAi) is an evolutionarily conserved process of gene silencing that has become a powerful tool for investigating gene function by reverse genetics. Here we describe the delivery of cassettes expressing hairpin RNA targeting green fluorescent protein (GFP) using Moloney leukemia virus-based and lentivirus-based retroviral vectors. Both transformed cell lines and primary dendritic cells, normally refractory to transfection-based gene transfer, demonstrated stable silencing of targeted genes, including the tumor suppressor gene TP53 in normal human fibroblasts. This report demonstrates that both Moloney leukemia virus and lentivirus vector-mediated expression of RNAi can achieve effective, stable gene silencing in diverse biological systems and will assist in elucidating gene functions in numerous cell types including primary cells.

Dendritic Cells↗
PubMed2006

Conversion of pre-RISC to holo-RISC by Ago2 during assembly of RNAi complexes.

In the Drosophila RNA interference (RNAi) pathway, small interfering RNAs (siRNAs) direct Argonaute2 (Ago2), an endonuclease, within the RNA-induced silencing complex (RISC) to cleave complementary mRNA targets. In vitro studies have shown that, for each siRNA duplex, RISC retains only one strand, the guide, and releases the other, the passenger, to form a holo-RISC complex. Here, we have isolated a new Ago2 mutant allele and provide, for the first time, in vivo evidence that endogenous Ago2 slicer activity is important to mount an RNAi response in Drosophila. We demonstrate in vivo that efficient removal of the passenger strand from RISC requires the cleavage activity of Ago2. We have also identified a new intermediate complex in the RISC assembly pathway, pre-RISC, in which Ago2 is stably bound to double-stranded siRNA.

Alleles↗
PubMed2025

RNAi screening of uncharacterized genes identifies promising druggable targets in Schistosoma japonicum.

Schistosomiasis affects more than 250 million people worldwide and is one of the neglected tropical diseases. Currently, the treatment of schistosomiasis relies on a single drug-praziquantel-which has led to increasing pressure from drug resistance. Therefore, there is an urgent need to find new treatments. The development of genome sequencing has provided valuable information for understanding the biology of schistosomes. In the genome of Schistosoma japonicum, approximately 11% of the protein-coding sequences are uncharacterized genes (UGs) annotated as "hypothetical protein" or "protein of unknown function." These poorly understood genes have been unjustifiably neglected, although some may be essential for the survival of the parasites and serve as potential drug targets. In this study, we systematically mined the highly expressed UGs in both genders of this parasite throughout key developmental stages in their mammalian host, using our previously published S. japonicum genome and RNA-seq data. By employing in vitro RNA interference (RNAi), we screened 126 UGs that lack homologs in Homo sapiens and identified 8 that are essential for the parasite vitality. We further investigated two UGs, Sjc_0002003 and Sjc_0009272, which resulted in the most severe phenotypes. Fluorescence in situ hybridization demonstrated that both genes were expressed throughout the body without sex bias. Silencing either Sjc_0002003 or Sjc_0009272 reduced the cell proliferation in the body. Furthermore, in vivo RNAi indicated both genes are required for the growth and survival of the parasites in the mammalian host. For Sjc_0002003, we further characterize the underlying molecular cause of the observed phenotype. Through RNA-seq analysis and functional studies, we revealed that silencing Sjc_0002003 reduces the expression of a series of intestinal genes, including Sjc_0007312 (hypothetical protein), Sjc_0008276 (vha-17), Sjc_0002942 (PLA2G15), and Sjc_0003646 (SJCHGC09134 protein), leading to gut dilation. Our work highlights the importance of UGs in schistosomes as promising targets for drug development in the treatment of the schistosomiasis.

Schistosoma japonicum↗
PubMed2026

IRES-like element-mediated translation of vsp1S4(-) suppresses BmCPV replication via RNAi antagonism.

Double-stranded RNA (dsRNA) viruses are thought to express proteins exclusively from their sense strand, while the antisense strand serves primarily as a replication template. Whether the antisense strand harbors hidden coding potential remains largely unexplored. Here, by integrating ribosome profiling and mass spectrometry, we identify a conserved 78-amino acid microprotein, vsp1S4(-), encoded by an antisense small open reading frame (sORFs) of the Bombyx mori cypovirus (BmCPV) genome. We demonstrate that vsp1S4(-) translation is driven by a previously unrecognized IRES-like element. Functional characterizations reveal that vsp1S4(-) localizes to the plasma membrane and acts as a negative regulator of viral replication. Mechanistically, vsp1S4(-) interacts directly with the viral RNAi suppressor NSP8, competitively disrupting the NSP8-AGO2 complex. This action restores the host's antiviral RNAi response, thereby limiting viral proliferation. Our findings challenge the conventional view of dsRNA virus coding capacity, unveil a novel viral immune evasion and replication control mechanism, and highlight antisense-encoded microproteins as potential targets for antiviral therapy.

Animals↗
PubMed2004

RNAi expression vectors in mammalian cells.

RNA interference (RNAi) is a recently developed technique for gene silencing by introducing dsRNA into cells, and it is shown to work in mammalian cells when siRNAs are used. Several groups have developed vector-based siRNA expression systems that can induce RNAi in living cells. These vector systems use a pol III promoter, such as U6 or H1, and are classified into two groups based on the form of expressed RNAs: tandem-type and hairpin-type. Here, we describe how to generate these siRNA expression vectors and outline the experimental procedure for suppressing the expression of a reporter gene by transient transfection of a siRNA expression vector.

Animals↗
PubMed2004

RNAi expression vectors in plant cells.

Suppression by double-stranded RNA (dsRNA) of expression of a target gene is known as RNA interference (RNAi). Tobacco BY-2 cell suspension has been used as a model cultured plant cell, because it is possible to produce populations of tobacco BY-2 cell suspensions that are uniform and divide synchronously for functional gene analysis. Here, we describe a method to induce RNAi by introducing a hairpin-type dsRNA expression vector into BY-2 cells via electroporation. This methodology should facilitate the analysis of individual gene function in plant cells.

Animals↗
PubMed2006

RNAi: for functional analysis and target validation.

The third annual conference on discovery on target, organised by the Cambridge Healthtech Institute was held on 19 - 20 October 2005, in Boston. More than 300 delegates from both academic and industrial institutes attended the meeting. The presentations provided insights into understanding the RNA interference technology as a useful tool to identify and validate new targets for therapeutic intervention. Discussions focused in the design of siRNA for effective gene silencing, RNAi screens to identify new targets, RNAi delivery and the in vivo validation of targets using this technology.

Animals↗
PubMed2004

The ins and outs of RNAi in mammalian cells.

The ability to utilize the RNA interference (RNAi) machinery for silencing target-gene expression has created a lot of excitement in the research community. RNAi in mammalian cells is achieved through introduction or expression of 21-23 bp small interfering RNAs (siRNAs) in cells or animals. Currently, there are six ways of producing siRNAs. siRNAs can be produced by chemical synthesis, in vitro transcription, or RNase III/Dicer digestion of long dsRNAs. Alternatively, they can be expressed in vivo from plasmids, PCR cassettes, or viral vectors that include a CMV or polymerase III (pol III) transcription unit. So far, these approaches have been used to create siRNAs for use in loss-of-function studies. However, it is clear that siRNAs also hold great promise as therapeutic tools. First, their activity seems to be very sequence-specific. Moreover, siRNAs could be modified in order to increase their stability and potency in vivo. Here, we will review the issues and findings related to siRNA design and production. Moreover, we will summarize new findings on siRNA specificity, modification, and delivery, which are critical to their use as therapeutic agents.

Animals↗
PubMed2005

Application of RNAi to cancer research and therapy.

The introduction of double-stranded RNA (dsRNA) into cells can effectively and specifically lead to the degradation of corresponding mRNAs in a gene-dependent manner, which is defined as RNA interfering (RNAi). This powerful technology has been widely employed to manipulate gene expression in mammalian and human cells, elucidate signal pathways and identify gene functions in a whole-genome scale. Simultaneously, many pharmaceutical companies are very interested in the research and development of RNAi-based drugs for various diseases, especially in cancers. In present review, we attempt to recapitulate the potential application of this breakthrough technology in many aspects of cancer gene therapy such as genome-scale screens, target identification and validation, functional analysis and animal models for diverse diseases.

Animals↗
PubMed2005

RNA interference (RNAi) for extracellular signal-regulated kinase 1 (ERK1) alone is sufficient to suppress cell viability in ovarian cancer cells.

While ovarian cancer is a leading cause of death in females today, the molecular, genetic, and environmental factors that initiate and support the progression of this disease are still only partially understood. The extracellular signal-regulated kinase (ERK) signaling pathway is a major contributor to cellular growth, differentiation and survival. Recently, we reported that this pathway is constitutively activated in ovarian cancer cells, and that by using RNA interference (RNAi) for ERK1 and ERK2, we were able to significantly suppress the number of viable tumor cells. In the present study, we have further investigated the mechanisms by which RNAi for the ERK kinases decreased viability in these cancer cells. It was determined that treatment of the cancer cells with small inhibitory RNAs (siRNAs) directed against ERK1 and ERK2 leads to the induction of apoptosis and necrosis by four hours following treatment. Additionally, we found that primary, nonmalignant ovarian cells do not respond similarly to ERK siRNA treatment and that these cells fail to die following treatment. Data presented show that ERK2 expression is more difficult to silence, depending upon cell type being examined and that silencing ERK1 expression alone is sufficient to significantly decrease tumor cell viability.

Apoptosis↗
PubMed2002

RNAi and viral vectors as useful tools in the functional genomics of plants. Construction of BMV-based vectors for RNA delivery into plant cells.

The sequencing of several complete genomes and the development of a DNA microarray technology are among the most important achievements of molecular biology. They gave the proper grounds for the development of modern functional genomics. However, there is one additional condition which needs to be satisfied to truely enable the study of how a genome works: a suitable method of selectively inducing and silencing the expression of each individual gene. The methods used so far have usually only permitted the influencing of gene expression through genetic manipulations at the DNA level (genetically modified plants). The discovery of RNA interference (RNAi) opens up completely new possibilities of research on the functioning of particular plant genes, without the necessity of altering the genome structure. In this case, interference takes place at the transcript level. Thus, at any given moment during plant development, the expression of a specific gene (or several genes) can be inhibited, even if it is important for the survival of the organism under study. To this end, a double-stranded RNA inducing the RNAi phenomenon has to be delivered into the plant cell. Here we describe the construction of four brome mosaic virus-based vectors, which, as our preliminary data indicate, can be used to transfer RNA into barley cells.

Bromovirus↗
PubMed2003

Antisense and RNAi: powerful tools in drug target discovery and validation.

Drug target discovery and validation are complex processes that require significant resource investments and impose a substantial economic burden on the pharmaceutical industry. Technologies that accelerate or enhance the precision of target selection are, therefore, in high demand. Traditional antisense and RNA interference (RNAi) technologies are powerful tools with applications in multiple phases of drug target discovery and validation. These approaches elicit potent and highly selective cleavage of a target mRNA, permitting evaluation of the role of the corresponding protein based on a loss-of-function phenotype. Incorporation of these technologies into high-throughput screens, in vitro biological assays and in vivo disease models provides valuable insight into gene function. Efforts are also underway to develop these agents as drugs. This review presents recent studies involving antisense and RNAi, and discusses how these technologies are facilitating target selection at various stages of the drug development process.

Animals↗
PubMed2005

State-of-the-art modified RNAi compounds for therapeutics.

In recent years, the recognition of non-protein coding RNAs as a functional effector of genetic expression has been highlighted by the discovery of RNA interference (RNAi). RNAi is an intracellular phenomenon that enables the eukaryotic cell to utilize double-stranded RNA molecules to silence gene expression in a sequence-specific manner. The short interfering RNA (siRNA) pathway has been intensively investigated and continues to serve as the basis for the development of potent molecular genetic tools. The power of this technology is most clearly evidenced by the fact that siRNA effector molecules can be chemically synthesized and exogenously delivered to specifically target and silence any gene of choice. This capability enables not only basic research, but also opens the door to a new therapeutic modality. Furthermore, the introduction of certain chemical modifications to siRNA effectors can produce a more robust knockdown of gene expression, hence, optimizing serum stability and increasing target specificity yet limiting the induction of cellular stress response, which are key features for in vivo delivery and successful therapeutics. This article outlines the progress in the development of differentially modified siRNA duplexes and their potential role as human therapeutics.

Animals↗
PubMed2005

[Effect of RNAi-mediated survivin gene silencing on apoptosis of ovarian cancer cell lines SKOV3 and SKOV3/ADM].

BACKGROUND & OBJECTIVE: RNA interference (RNAi) has been widely used in tumor gene therapy, antivirus, and gene drug selection. Survivin gene is highly expressed in ovarian cancer cell line SKOV3 and drug-resistant cell line SKOV3/ADM, and is an ideal target of gene therapy for ovarian cancer. This study was to explore effect of RNAi-mediated Survivin gene silencing on apoptosis of SKOV3 and SKOV3/ADM cells. METHODS: Recombinant plasmid pshRNA-Survivin was transfected into SKOV3 and SKOV3/ADM cells. The expression of Survivin was detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The apoptosis of SKOV3 and SKOV3/ADM cells after transfection were evaluated by AO/EB dyeing, TUNEL, and flow cytometry. RESULTS: After transfection of pshRNA-Survivin, mRNA and protein levels of Survivin gene in SKOV3 and SKOV3/ADM cells were obviously reduced; the apoptosis of SKOV3 and SKOV3/ADM cells were significantly higher in transfection group than in control group (P0.01); 48 h after transfection, the apoptosis rate was 14.05% in SKOV3 cells, and 21.02% in SKOV3/ADM cells, no obvious apoptosis was detected in control cells. CONCLUSION: pshRNA-Survivin could reduce the expression of Survivin gene, and induce apoptosis of SKOV3 and SKOV3/ADM cells.

Antineoplastic Agents↗
PubMed2005

[RNA interference (RNAi) as novel approach for gene silencing--review].

RNA interference (RNAi), a highly conserved evolutionary process of post-transcriptional gene silencing, can be triggered by small interfering RNAs (siRNAs) that mediate sequence-specific mRNA degradation. The article summarized some aspects of the mechanism of RNAi, siRNA design and delivery of siRNAs to mammalian somatic cells. And some hurdles in practice were also discussed.

Animals↗
PubMed2006

From genome to phenome--RNAi library screening and hit characterization using signaling pathway analysis.

Comprehensive, high-throughput analysis of gene function using RNA interference (RNAi)-based screens is emerging as a significant step forward for preliminary drug-target identification. Until quite recently drug target identification depended heavily on the analysis of changes in gene expression, which in turn needed to be correlated with gene function. The promise of obtaining preliminary 'gene to phenotype' information using a single high-throughput platform is propelling major investment in this area by biotechnology and pharmaceutical companies. This review discusses recent developments in the use of RNAi library screens, and the various assay formats and techniques currently in use for data analysis downstream of such screens.

Animals↗
PubMed2006

Antiviral applications of RNAi.

RNA interference (RNAi) is a natural mechanism by which small interfering RNA (siRNA) operates to specifically and potently downregulate the expression of a target gene. This downregulation has been thought to predominantly function at the level of mRNA, as post-transcriptional gene silencing. The discovery that siRNAs can suppress gene expression at the level of transcription, that is, transcriptional gene silencing, has created a major paradigm shift in mammalian RNAi. These findings significantly broaden the role that RNA, specifically siRNA and potentially microRNA, plays in the regulation of gene expression, as well as the breadth of potential siRNA target sites. Indeed, the specificity and simplicity of design makes the use of siRNAs to target and suppress virtually any gene of interest a realized technology. Furthermore, since siRNAs are small nucleic acid reagents, they are unlikely to elicit an immune response, theoretically making them good therapeutics. The development, delivery and potential therapeutic use of antiviral siRNAs in treating viral infections and emerging viral threats are reviewed.

Animals↗