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PubMed2006

Oncopeltus fasciatus zen is essential for serosal tissue function in katatrepsis.

Unlike most Hox cluster genes, with their canonical role in anterior-posterior patterning of the embryo, the Hox3 orthologue of insects has diverged. Here, we investigate the zen orthologue in Oncopeltus fasciatus (Hemiptera:Heteroptera). As in other insects, the Of-zen gene is expressed extraembryonically, and RNA interference (RNAi) experiments demonstrate that it is functionally required in this domain for the proper occurrence of katatrepsis, the phase of embryonic movements by which the embryo emerges from the yolk and adjusts its orientation within the egg. After RNAi knockdown of Of-zen, katatrepsis does not occur, causing embryos to complete development inside out. However, not all aspects of expression and function are conserved compared to grasshopper, beetle, and fly orthologues. Of-zen is not expressed in the extraembryonic tissue until relatively late, suggesting it is not involved in tissue specification. Within the extraembryonic domain, Of-zen is expressed in the outer serosal membrane, but unlike orthologues, it is not detectable in the inner extraembryonic membrane, the amnion. Thus, the role of zen in the interaction of serosa, amnion, and embryo may differ between species. Of-zen is also expressed in the blastoderm, although this early expression shows no apparent correlation with defects seen by RNAi knockdown.

Amino Acid Sequence↗

PubMed2002

Rescue of polyglutamine-mediated cytotoxicity by double-stranded RNA-mediated RNA interference.

RNA interference (RNAi) is a mechanism that appears to control unwanted gene expression in a wide range of species. In Drosophila, RNAi is most effectively induced by double-stranded RNAs (dsRNAs) of over approximately 80 nucleotides (nt) and in mammalian cells an RNAi-like inhibition of gene expression has been shown to be mediated by dsRNAs of approximately 21-23 nt. To test if RNAi can be used to specifically down-regulate a human disease-related transcript we have used Drosophila and human tissue culture models of the dominant genetic disorder spinobulbar muscular atrophy (SBMA). A variety of different dsRNAs were assessed for the ability to inhibit expression of transcripts that included a truncated human androgen receptor (ar) gene containing different CAG repeat lengths (16-112 repeats). In Drosophila cells, dsRNAs corresponding to non-repetitive sequences mediated a high degree of sequence-specific inhibition, whereas RNA duplexes containing CAG repeat tracts only induced gene-specific inhibition when flanking ar sequences were included; dsRNAs containing various lengths of CAG repeats plus ar sequences were unable to induce allele-specific interference. In mammalian cells we tested sequence-specific small dsRNAs of 22 nt; these rescued the toxicity and caspase-3 activation induced by plasmids expressing a transcript encoding an expanded polyglutamine tract. This study demonstrates the feasibility of targeting a transcript associated with an important group of genetic diseases by RNAi.

Animals↗

PubMed2003

A transient RNA interference assay system using Arabidopsis protoplasts.

Double-stranded RNA (dsRNA) induces sequence-specific gene silencing in eukaryotes through a process known as RNA interference (RNAi). RNAi is now used as a powerful tool for functional genomics in many eukaryotes, including plants. We herein report a dsRNA-mediated transient RNAi assay system using protoplasts from Arabidopsis mesophyll cells and suspension-cultured cells (cell line T87). Introduction of dsRNA into protoplasts led to marked silencing of target transgenes. Our assay system would provide a convenient and efficient way to induce RNAi in protoplasts of the model plant Arabidopsis thaliana.

Arabidopsis↗

PubMed2003

Tachykinin dysfunction attenuates monocrotaline-induced pulmonary hypertension.

We explored the dysfunction of tachykinins on monocrotaline (MCT)-induced pulmonary hypertension by using double-stranded preprotachykinin (ds PPT) RNA and neurokinin receptor (NK) antagonists. Here, we showed the possibility to attenuate the PPT gene expression by ds RNA, RNA interference (RNAi), in fully developed tissue of rats. We designed four groups (control, MCT, RNAi + MCT, and solvent + MCT) of experiments in series 1 and seven groups (control, MCT, MCT + CP-96345-3.4, MCT + CP-96345-10, MCT + CP-96344-10, MCT + SR-48968, and MCT + SR-48965) of experiments in series 2. Rats in the control groups received saline injection. MCT-treated rats received a single MCT injection (60 mg/kg sc). One day prior to MCT, bilateral nodose ganglia were microinjected with ds PPT RNA in rats of the RNAi + MCT group or with solvent in the solvent + MCT group. Beginning from 1 day post-MCT, MCT-treated rats received a daily injection of the NK(1) receptor antagonist, CP-96345 (3.4 or 10 mg/kg ip) or its inactive enantiomer CP-96344 (10 mg/kg ip). The NK(2) receptor antagonist SR-48968 (3 mg/kg ip) or its inactive enantiomer SR-48965 (3 mg/kg ip) was injected to MCT-treated rats every other day starting 1 day post-MCT. Functional study was carried out 2 weeks (series 1) or 3 weeks (series 2) after MCT. MCT induced right ventricular hypertrophy, as well as increases in pulmonary arterial pressure, PPT mRNA (nodose ganglia and lung tissue), and lung tissue substance P level. All of the above MCT-induced alterations were attenuated by either RNAi or NK receptor antagonists. We conclude that tachykinins play an important role in MCT-induced pulmonary hypertension.

Animals↗

PubMed2006

Inhibition of measles virus and subacute sclerosing panencephalitis virus by RNA interference.

Subacute sclerosing panencephalitis (SSPE) is a rare, but fatal outcome of measles virus (MeV) infection. SSPE develops after prolonged persistence of mutated MeV called SSPE virus. Although a combination therapy using interferon and inosiplex or ribavirin appears to prolong survival time to some extent, there is currently no effective treatment to completely cure SSPE and a new treatment strategy is greatly needed. In this study, we adopted RNA interference (RNAi) strategy and examined whether small interfering RNAs (siRNAs) can be used to inhibit replication of MeV and SSPE virus. We report here that siRNAs targeted against L mRNA of MeV, either synthetic siRNAs or those generated by pcPUR+U6i-based expression plasmids, effectively and specifically inhibited replication of both MeV and SSPE virus without exhibiting any cytotoxic effect. The L protein of MeV is a major component of RNA-dependent RNA polymerase that is essential for viral RNA replication, and yet it is least abundant among all the MeV proteins expressed. Therefore, mRNA encoding the L protein would be a good target for RNAi strategy. The present results imply the possibility that our siRNAs against MeV L mRNA are among the potential candidates to be used to treat patients with SSPE.

Animals↗

PubMed2003

Gene silencing in mammalian cells by PCR-based short hairpin RNA.

RNA interference (RNAi) provides a powerful tool to silence genes in a sequence-specific manner in a variety of systems. However, not all sequences are effective in the RNAi-mediated gene silencing. In this study, we developed a polymerase chain reaction (PCR)-based RNAi strategy for a quick screening of small interfering RNA (siRNA) efficiency. This method utilized a two-step PCR to generate a chimeric DNA template containing the U6 promoter or cytomegalovirus promoter and short hairpin DNA. We demonstrated that the transfection of the PCR products into mammalian cells resulted in specific depressions of exogenous (luciferase, green fluorescent protein and beta-galactosidase) and endogenous (annexin II) gene expressions. This PCR strategy provides a rapid, easy and cheap approach for testing candidates siRNA sequences and is an attractive alternative to subcloning.

Animals↗

PubMed2004

Loss of XIAP protein expression by RNAi and antisense approaches sensitizes cancer cells to functionally diverse chemotherapeutics.

Stable expression of short-hairpin RNAs (shRNAs) directed against the X-linked inhibitor of apoptosis (XIAP) resulted in the generation of three MDA-MB-231 cell lines (XIAP shRNA cells) with reductions in XIAP mRNA and protein levels > 85% relative to MDA-MB-231 cells stably transfected with the U6 RNA polymerase III promoter alone (U6 cells). This RNA interference (RNAi) approach dramatically sensitized these cells to killing by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Importantly, loss of XIAP also sensitized the cells to killing by taxanes but had no additional effects on killing by carboplatin and doxorubicin. The increased sensitivity of the XIAP shRNA cells to killing by TRAIL and taxanes correlated with enhanced caspase cleavage and activation, including caspase-8, and robust processing of poly(ADP-ribose) polymerase and BID compared to U6 cells. Additionally, increasing XIAP levels by adenovirus-mediated expression protected both XIAP shRNA and U6 cells from TRAIL killing in a dose-dependent manner. The effects observed by stable RNAi with respect to TRAIL sensitization were also achieved following downregulation of XIAP in Panc-1 cells treated with a second-generation, mixed-backbone antisense oligonucleotide, AEG 35156/GEM640. These data indicate that reducing XIAP protein expression by either RNAi or antisense approaches increases cancer cell susceptibility to functionally diverse chemotherapeutic agents and supports the notion that downregulation of XIAP in vivo may synergize with disease-relevant chemotherapeutic regimes, including TRAIL and taxanes, to increase the effectiveness of antineoplastic agents.

Antisense Elements (Genetics)↗

PubMedDate not supplied

Silencing of the HER2/neu gene by siRNA inhibits proliferation and induces apoptosis in HER2/neu-overexpressing breast cancer cells.

In eukaryotes, double-stranded (ds) RNA induces sequence-specific inhibition of gene expression referred to as RNA interference (RNAi). We exploited RNAi to define the role of HER2/neu in the neoplastic proliferation of human breast cancer cells. We transfected SK-BR-3, BT-474, MCF-7, and MDA-MB-468 breast cancer cells with short interfering RNA (siRNA) targeted against human HER2/neu and analyzed the specific inhibition of HER2/neu expression by Northern and Western blots. Transfection with HER2/neu-specific siRNA resulted in a sequence-specific decrease in HER2/neu mRNA and protein levels. Moreover, transfection with HER2/neu siRNA caused cell cycle arrest at G0/G1 in the breast cancer cell lines SK-BR-3 and BT-474, consistent with a powerful RNA silencing effect. siRNA treatment resulted in an antiproliferative and apoptotic response in cells overexpressing HER2/neu, but had no influence in cells with almost no expression of HER2/neu proteins like MDA-MB-468 cells. These data indicate that HER2/neu function is essential for the proliferation of HER2/neu-overexpressing breast cancer cells. Our observations suggest that siRNA targeted against human HER2/neu may be valuable tools as antiproliferative agents that display activity against neoplastic cells at very low doses.

Apoptosis↗

PubMed2006

RNAi components are required for nuclear clustering of Polycomb group response elements.

Drosophila Polycomb group (PcG) proteins silence homeotic genes through binding to Polycomb group response elements (PREs). Fab-7 is a PRE-containing regulatory element from the homeotic gene Abdominal-B. When present in multiple copies in the genome, Fab-7 can induce long-distance gene contacts that enhance PcG-dependent silencing. We show here that components of the RNA interference (RNAi) machinery are involved in PcG-mediated silencing at Fab-7 and in the production of small RNAs at transgenic Fab-7 copies. In general, these mutations do not affect the recruitment of PcG components, but they are specifically required for the maintenance of long-range contacts between Fab-7 copies. Dicer-2, PIWI, and Argonaute1, three RNAi components, frequently colocalize with PcG bodies, and their mutation significantly reduces the frequency of PcG-dependent chromosomal associations of endogenous homeotic genes. This suggests a novel role for the RNAi machinery in regulating the nuclear organization of PcG chromatin targets.

Animals↗

PubMed2005

Inhibition of Marburg virus protein expression and viral release by RNA interference.

High mortality rates and lack of an available vaccine against Marburg haemorrhagic fever (MHF) highlight the need for a defensive therapy against MHF and greater knowledge of the causative agent, the Marburg virus (MARV). Here, RNA interference (RNAi) is employed to destroy MARV transcripts, disrupting replication and allowing analysis of various roles of MARV proteins. Small interfering RNAs (siRNAs) homologous to three MARV transcripts (NP, VP35 and VP30) were co-transfected into cells with plasmids encoding the corresponding nucleocapsid proteins. The resulting decrease in MARV nucleocapsid-protein levels was shown to be specific, as siRNA that was not homologous to the MARV genome did not decrease the levels of viral nucleocapsid proteins. Additionally, transcript levels of double-stranded RNA (dsRNA)-sensor proteins, the dsRNA-activated protein kinase and 2',5'-oligoadenylate synthetase 1 remained unchanged, suggesting that the decrease in viral proteins was not a result of activation of the antiviral properties of the interferon system. Subsequently, siRNAs were shown to reduce intracellular viral proteins in MARV-infected cells and viral material released into the medium. Targeted reduction of VP30 downregulated the intracellular levels of all other viral proteins, suggesting that VP30 plays an essential role for transcription/replication. The efficient reduction of MARV replication also suggests that RNAi may provide an agent against MHF.

Animals↗

PubMed2006

[Experimental research of therapeutic effect on hepatocellular carcinoma of targeting SMYD3 gene inhibition by RNA interference].

OBJECTIVE: To determine the potential of SMYD3 as a therapeutic target for hepatocellular carcinoma (HCC) by potent and highly sequence-specific RNA interference (RNAi) technique. METHODS: The mRNA of SMYD3 was detected by RT-PCR in different HCC cell lines, such as HepG2, Hep3B and SMMC7721. Recombinant SMYD3 shRNA plasmid Pgenesil-1-s was constructed and transfected into HepG2 cells, and Western blot was used to identify the down regulation of SMYD3 protein expression after transfection. MTT and flow cytometry analysis (FCM) were respectively applied to analysis cell proliferation and apoptosis. In vivo study was carried out by injecting recombinant SMYD3 shRNA plasmids into transplanted tumors of nude mice. RESULTS: The expression of SMYD3 mRNA was abundant in HCC cell lines HepG2, Hep3B, SMMC7721, whereas none in normal hepatic cell line L-02. RNA interference was able to suppress SMYD3 expression greatly and then inhibited cell growth effectively and induced apoptosis of HepG2 cells efficiently. After injection of recombinant SMYD3 shRNA plasmid, transplanted tumors grew slowly and reduced in size and weight when compared with those of control groups (P < 0.01). CONCLUSIONS: SMYD3 plays a major role in occurrence and progress of HCC. Inhibition of SMYD3 by RNAi can induce apoptosis in HepG2 cells and suppress tumor growth in nude mice. Therefore SMYD3 could be an ideal therapeutic target for HCC.

Animals↗

PubMed2006

Argonaute-1 directs siRNA-mediated transcriptional gene silencing in human cells.

Argonaute proteins are the core components of effector complexes that facilitate RNA interference (RNAi). Small interfering RNAs (siRNAs) targeted to promoter regions mediate transcriptional gene silencing (TGS) in human cells through heterochromatin formation. RNAi effector complexes have yet to be implicated in the mechanism of mammalian TGS. Here we describe the role of the human Argonaute-1 homolog (AGO1) in directing TGS at the promoters for human immunodeficiency virus-1 coreceptor CCR5 and tumor suppressor RASSF1A. AGO1 associates with RNA polymerase II (RNAPII) and is required for histone H3 Lys9 dimethylation and TGS. AGO1, TAR RNA-binding protein-2 (7TRBP2) and Polycomb protein EZH2 colocalize to the siRNA-targeted RASSF1A promoter, implicating Polycomb silencing in the mechanism of mammalian TGS. These results establish a connection between RNAi components AGO1 and TRBP2, RNAPII transcription and Polycomb-regulated control of gene expression.

Argonaute Proteins↗

PubMed2004

RNAi-mediated Hip1R silencing results in stable association between the endocytic machinery and the actin assembly machinery.

Actin filaments transiently associate with the endocytic machinery during clathrin-coated vesicle formation. Although several proteins that might mediate or regulate this association have been identified, in vivo demonstration of such an activity has not been achieved. Huntingtin interacting protein 1R (Hip1R) is a candidate cytoskeletal-endocytic linker or regulator because it binds to clathrin and actin. Here, Hip1R levels were lowered by RNA interference (RNAi). Surprisingly, rather than disrupting the transient association between endocytic and cytoskeletal proteins, clathrin-coated structures (CCSs) and their endocytic cargo became stably associated with dynamin, actin, the Arp2/3 complex, and its activator, cortactin. RNAi double-depletion experiments demonstrated that accumulation of the cortical actin-endocytic complexes depended on cortactin. Fluorescence recovery after photobleaching showed that dynamic actin filament assembly can occur at CCSs. Our results provide evidence that Hip1R helps to make the interaction between actin and the endocytic machinery functional and transient.

Actin Cytoskeleton↗

PubMed2026

Genome-wide identification of neuropeptides from Plutella xylostella (Lepidoptera: Plutellidae) and elucidating the essential roles of adipokinetic hormone in lipid mobilisation and food intake.

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a major pest of cruciferous crops and has developed high levels of resistance to many widely used insecticides. Neuropeptides are involved in regulating essential insect biological processes, which could be considered potential target genes for pest control. In this study, a total of 45 neuropeptide precursor genes were identified in the genome of P. xylostella, including two adipokinetic hormone genes (PxAKH1 and PxAKH2). The qPCR analysis showed that PxAKH genes were highly expressed in third- and fourth-instar larvae and exhibited high expression levels in the fat body, head, and gut of P. xylostella larvae. Additionally, short-term starvation stimulated food consumption in P. xylostella, which was consistent with the significant induction of PxAKH1 within 6 h. Subsequently, RNA interference (RNAi) was utilised to investigate the functions of PxAKH1 in P. xylostella, and the injection of dsPxAKH1 significantly suppressed target gene expression, achieving a maximum silencing efficiency of 73.03%. Notably, knockdown of PxAKH1 increased triacylglycerol levels from 23.67 ± 0.56 mg/g in the dsGFP control to 25.84 ± 0.64 mg/g and enhanced lipid storage, while markedly reducing food intake from 221.33 ± 9.10 mm2 to 123.33 ± 18.80 mm2 in P. xylostella larvae. In summary, these findings demonstrate that PxAKH1 plays a critical role in regulating lipid mobilisation and food intake in P. xylostella, indicating its potential as an RNAi-based target for pest control.

RNA interference↗

PubMed2005

Enhancing siRNA effects in T cells for adoptive immunotherapy.

Genetically manipulated T cells can be endowed with novel functions to obtain desired in vivo effects after adoptive transfer. This genetic approach is being used to introduce genes such as chimeric immunoreceptors and tumor-specific T cells are being evaluated in early phase clinic trials. However, the ability to alter the genetic programming of T cells also presents opportunities to remove unwanted T-cell functions in order to augment an anti-tumor effect or endow resistance such as to HIV infection. Specifically, the use of RNA interference (RNAi) to disrupt gene expression by targeting either the mRNA or the promoter, provides investigators with many new opportunities to genetically modify T cells that should prove useful in future applications of adoptive immunotherapy.

Animals↗

PubMed2006

Transcriptional and phenotypic comparisons of Ppara knockout and siRNA knockdown mice.

RNA interference (RNAi) has great potential as a tool for studying gene function in mammals. However, the specificity and magnitude of the in vivo response to RNAi remains to be fully characterized. A molecular and phenotypic comparison of a genetic knockout mouse and the corresponding knockdown version would help clarify the utility of the RNAi approach. Here, we used hydrodynamic delivery of small interfering RNA (siRNA) to knockdown peroxisome proliferator activated receptor alpha (Ppara), a gene that is central to the regulation of fatty acid metabolism. We found that Ppara knockdown in the liver results in a transcript profile and metabolic phenotype that is comparable to those of Ppara-/- mice. Combining the profiles from mice treated with the PPARalpha agonist fenofibrate, we confirmed the specificity of the RNAi response and identified candidate genes proximal to PPARalpha regulation. Ppara knockdown animals developed hypoglycemia and hypertriglyceridemia, phenotypes observed in Ppara-/- mice. In contrast to Ppara-/- mice, fasting was not required to uncover these phenotypes. Together, these data validate the utility of the RNAi approach and suggest that siRNA can be used as a complement to classical knockout technology in gene function studies.

Animals↗

PubMed2004

Exogenous siRNA mediates sequence-independent gene suppression by signaling through toll-like receptor 3.

RNA interference (RNAi) is a powerful method that specifically suppresses gene expression in a sequence-dependent manner whose machinery is found in organisms from fungi to mammals. Mammalian cells have developed a sequence-independent system of gene suppression often induced by viral replication that includes the recognition of double-stranded RNA (dsRNA) through Toll-like receptor 3 (TLR3) and induction of type I interferon synthesis. Interferon activates the transcription of a set of genes including dsRNA-activated protein kinase that suppresses protein synthesis and 2'-5'-oligoadenylate synthetase, which generates a product that activates RNase L to cleave RNA in a sequence-independent manner. We observed that 21-bp dsRNA, a key mediator of RNAi, not only induces sequence-specific gene suppression, but also signals TLR3 to induce type I interferon and activates sequence-independent suppression of protein synthesis and enhancement of mRNA degradation. This sequence-independent suppression was demonstrated for both an exogenously administered reporter gene as well as during the targeting of viral genes in the course of acute herpes simplex virus type I infection of keratinocytes. As TLR3 is expressed by many primary cell types and cell lines, this sequence-independent suppression should be considered in the design of experiments using small interfering RNA-mediated gene suppression.

Cell Line↗

PubMed2006

Functional replacement of Trypanosoma brucei Argonaute by the human slicer Argonaute2.

RNA interference (RNAi) is widespread throughout the eukaryotic lineage, from protozoa to man. Central to all RNAi phenomena is a member of the Argonaute protein family, and, in the case of dsRNA-triggered mRNA cleavage, the Ago protein functions as the RNAi endonuclease or slicer. However, at present there is no definite experimental evidence that slicer Argonautes can be interchanged between distantly related organisms. Here, we show that the human slicer Argonaute2 (HsAgo2), but not HsAgo1, functions in RNAi in the early divergent protozoan Trypanosoma brucei, thus mimicking the situation in mammalian cells. This finding indicates that the basic features of the RNAi mechanism are conserved from T. brucei to man.

Animals↗