PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Small interfering RNA”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 271 records · Page 15Linked to original sources

Double transfection improves small interfering RNA-induced thrombin receptor (PAR-1) gene silencing in DU 145 prostate cancer cells.

The efficiency of small interfering RNA (siRNA)-induced gene knockdown is hampered by low transfection efficiency. We established a novel and simple double transfection method using specific siRNA duplexes targeted against human thrombin receptor PAR-1 in DU 145 prostate cancer cells. The initial siRNA transfection of cell suspensions followed by re-transfection of adherent cells on the following day resulted in undetectable PAR-1 mRNA and absent receptor protein. PAR-1 mRNA expression was silenced for up to five days. Functional studies showed that PAR-1 gene silencing in DU 145 cells abolished the modulating effects of thrombin on cell adhesion to the extracellular matrix proteins, fibronectin and laminin, thus demonstrating the essential role of PAR-1 in mediating thrombin effects on DU 145 cell adhesion.

Base Sequence↗

BAP31 is involved in the retention of cytochrome P450 2C2 in the endoplasmic reticulum.

Microsomal cytochrome P450 2C2 is an integral endoplasmic reticulum (ER) membrane protein that is directly retained in the ER and excluded from transport vesicles. We have used bimolecular fluorescence complementation and co-immunoprecipitation to show that a ubiquitous ER membrane protein (BAP31) interacts with P450 2C2 in transfected COS-1 cells. A chimera containing only the N-terminal signal anchor of P450 2C1 (P450 2C1-(1-29)) also interacted with BAP31, which is consistent with interaction of the two proteins via their transmembrane domains. Down-regulation of BAP31 expression with small interfering RNA resulted in redistribution of green fluorescent protein-tagged P450 2C2 or P450 2C1-(1-29) from the ER into the nuclear membrane and compact perinuclear compartment structures as well as the cell surface in a small fraction of the cells. In Bap31-null embryonic stem cells, a significant fraction of P450 2C2 or P450 2C1-(1-29) was detected at the cell surface and nuclear envelope, but was redistributed to the ER by expression of BAP31. The expression level of P450 2C2 was significantly increased in COS-1 cells with repressed levels of BAP31. Formation of the pro-apoptotic p20 fragment of BAP31 was detected in transfected COS-1 cells expressing P450 2C2, and annexin V staining was consistent with the activation of an apoptotic pathway in these cells. Down-regulation of BAP31 with small interfering RNA partially reversed the apoptosis. These results suggest that interaction of P450 2C2 with BAP31 is important for its ER retention and expression level and that BAP31 may be involved in the regulation of apoptosis induced by the ER overload response to increased expression of P450.

Animals↗

siRNA, miRNA and HIV: promises and challenges.

Small interfering RNA (siRNA) and microRNA (miRNA) are small RNAs of 18-25 nucleotides (nt) in length that play important roles in regulating gene expression. They are incorporated into an RNA-induced silencing complex (RISC) and serve as guides for silencing their corresponding target mRNAs based on complementary base-pairing. The promise of gene silencing has led many researchers to consider siRNA as an anti-viral tool. However, in long-term settings, many viruses appear to escape from this therapeutical strategy. An example of this may be seen in the case of human immunodeficiency virus type-1 (HIV-1) which is able to evade RNA silencing by either mutating the siRNA-targeted sequence or by encoding for a partial suppressor of RNAi (RNA interference). On the other hand, because miRNA targeting does not require absolute complementarity of base-pairing, mutational escape by viruses from miRNA-specified silencing may be more difficult to achieve. In this review, we discuss stratagems used by various viruses to avoid the cells' antiviral si/mi-RNA defenses and notions of how viruses might control and regulate host cell genes by encoding viral miRNAs (vmiRNAs).

HIV↗

siRNA targeting LMP1-induced apoptosis in EBV-positive lymphoma cells is associated with inhibition of telomerase activity and expression.

Epstein-Barr Virus (EBV) is closely associated with B cell malignancies. However, whether EBV appears to be absolutely required for cell proliferation and survival in lymphoma cells is still unknown. In this study, small interfering RNA (siRNA) targeting LMP1 was employed to investigate the effect of LMP1 on cell proliferation in EBV-positive lymphoblastoid B-cell line. A plasmid stable encoding 21-nt small RNA specifically and efficiently interfering LMP1 was constructed, resulting in a substantial loss of LMP1 mRNA and a significantly decreased LMP1 protein expression. Our data demonstrated that cell proliferation was completely inhibited and apoptosis was induced after knockdown of LMP1 gene in lymphoblastoid B-cell line. Also, we found that suppression of LMP1 caused downregulation of telomerase protein expression and decreased telomerase activity in lymphoma cells. In EBV-negative NPC cell line, transfection of plasmid expressing LMP1 greatly enhanced telomerase protein expression. Our results suggested that siRNA targeting LMP1 can induce apoptosis in EBV-positive lymphoma cells and is associated with inhibition of telomerase activity and expression. siRNA-directed LMP1 silencing may be of the therapeutic value for preventing and treating those EBV-associated tumors.

Animals↗

Small interfering RNA-induced suppression of MDR1 (P-glycoprotein) restores sensitivity to multidrug-resistant cancer cells.

Overexpression of P-glycoprotein (P-gp), the MDR1 gene product, confers multidrug resistance (MDR) to cancer cells. Clinically, MDR is one of the major causes for chemotherapeutic treatment failure in cancer patients. To explore a new approach to circumventing MDR, we adopted RNA interference to target MDR1 gene expression. RNA interference is a conserved biological response to double-stranded RNA, which results in sequence-specific gene silencing [G. J. Hannon, Nature (Lond.), 418: 244-251, 2002]. We report that introduction of an MDR1-targeted small interfering RNA duplex into drug-resistant cancer cells markedly inhibited the expression of MDR1 mRNA and P-gp, as determined by reverse transcription-PCR and Western blot. Inhibition of P-gp expression by small interfering RNA enhanced the intracellular accumulation of and selectively restored sensitivity to drugs transported by P-gp. These studies indicate that RNA interference can modulate MDR in preclinical models.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

RNAi-based knockdown of HBx mRNA in HBx-transformed and HBV-producing human liver cells.

RNA interference (RNAi) is the process of sequence-specific gene silencing induced by 21-23-nt RNA of small interfering RNA (siRNA). The HBx of hepatitis B virus (HBV) causing human liver diseases has been known as a multifunctional protein which affects transcription, cell growth, and apoptotic cell death. Here, we demonstrate that the HBx-specific siRNA (siRNAx) and short hairpin RNA (shRNAx) effectively induce the degradation of HBx mRNA in HBx-transformed and HBV-producing human liver cells by up to 80-90%. Also, the HBx expression in HBx-transformed cells was continuously silenced by retransformation with the shRNAx expression vector. These results imply that HBx-driven RNAi, either delivery of siRNAx or expression of shRNAx, provides a promising anti-HBV approach to suppress the HBx expression in human hepatoma cells.

Base Sequence↗

Down-regulation of IGF-IR using small, interfering, hairpin RNA (siRNA) inhibits growth of human lung cancer cell line A549 in vitro and in nude mice.

Type I insulin-like growth factor receptor (IGF-IR), which is frequently overexpressed in a variety of human cancers including lung cancer, mediates cancer cell proliferation and tumor growth. In this study, we used a human U6 promoter-driven DNA-template approach to induce hairpin RNA (hpRNA)-triggered RNAi to silence IGF-IR gene expression in the human lung cancer cell line A549, and then evaluate its effects on apoptosis, apoptosis-related gene expression, and the growth of tumor cells in vitro and in nude mice. IGF-IR expression levels were found to markedly decrease in cells transfected with a plasmid expressing hairpin siRNA for IGF-IR (by more than 78.9%). Down-regulation of IGR-IR concomitantly accompanied reduction of bcl-2 as well as pERK and pAkt levels, activation of caspase-3, apoptosis and growth inhibition of A549 cells in vitro. Direct intratumoral injections of plasmid DNA expressing hpRNA for IGF-IR significantly regressed pre-established tumors in nude mice. Our results support the therapeutic potential of RNAi as a method for gene therapy in treating lung cancer.

Animals↗

Towards therapy using RNA interference.

Small interfering RNA (siRNA) molecules are short sequences of double-stranded RNA 19-27 bp in length, which suppress expression of target genes by inducing the breakdown of the cognate mRNA through mechanisms that are still being elucidated. siRNA molecules can be chemically synthesized or prepared through digestion of larger double-stranded RNA molecules using recombinant dicer or RNAase III enzyme. siRNA molecules can also be encoded by plasmid or virus vectors or expressed in transgenic animals. Design of siRNA sequences that efficiently suppress target genes can sometimes be challenging, although digestion of large double-stranded RNA species with recombinant dicer or RNAase III may remove the necessity for testing multiple candidate siRNA. Exogenous siRNA can suppress translation for varying amounts of time depending on the half-life of the protein targeted. Vector-mediated approaches may improve duration but their use can be limited by the permanency and efficiency of transduction. Potential therapeutic targets for siRNA include viral and non-viral pathogens, cancer, neurodegenerative diseases, septic shock and macular degeneration. Suppression of expression via siRNA is also an extremely useful research tool for ascertaining gene function. Looking ahead to clinical applications, it will be important to know the consequences of inadvertent suppression of non-targeted sequences. If safety can be established, siRNA has the potential to significantly impact the field of molecular medicine.

Clinical Trials as Topic↗

Essential role of obscurin in cardiac myofibrillogenesis and hypertrophic response: evidence from small interfering RNA-mediated gene silencing.

Obscurin is a recently identified giant multidomain muscle protein (approximately 800 kDa) whose structural and regulatory functions remain to be defined. The goal of this study was to examine the effect of obscurin gene silencing induced by RNA interference on the dynamics of myofibrillogenesis and hypertrophic response to phenylephrine in cultured rat cardiomyocytes. We found that that the adenoviral transfection of short interfering RNA (siRNA) constructs targeting the first coding exon of obscurin sequence resulted in progressive depletion of cellular obscurin. Confocal microscopy demonstrated that downregulation of obscurin expression led to the impaired assembly of new myofibrillar clusters and considerable aberrations of the normal structure of the contractile apparatus. While the establishment of the initial periodic pattern of alpha-actinin localization remained mainly unaffected in siRNA-transfected cells, obscurin depletion did cause the defective lateral alignment of myofibrillar bundles, leading to their abnormal bifurcation, dispersal and multiple branching. Bending of immature myofibrils, apparently associated with the loss of their rigidity, a modified titin pattern, the absence of well-formed A-bands in newly formed contractile structures as documented by a diffuse localization of sarcomeric myosin labeling, and an occasional irregular periodicity of sarcomere spacing were typical of obscurin siRNA-treated cells. These results suggest that obscurin is indispensable for spatial positioning of contractile proteins and for the structural integration and stabilization of myofibrils, especially at the stage of myosin filament incorporation and A-band assembly. This demonstrates a vital role for obscurin in myofibrillogenesis and hypertrophic growth.

Actinin↗

The metastasis-associated gene S100A4 is a novel target of beta-catenin/T-cell factor signaling in colon cancer.

BACKGROUND & AIMS: Activation of the Wnt/beta-catenin pathway is frequently observed in colorectal cancers. Our aim was to elucidate the impact of gain-of-function beta-catenin on the metastasis-associated gene S100A4 in human colon cancer cell lines and tumors. METHODS: We analyzed cell lines heterozygous for gain-of-function and wild-type beta-catenin, and variants homozygous for gain- or loss-of-function mutation in beta-catenin, for S100A4 expression, cell motility, and in vivo metastasis. beta-catenin-mediated S100A4 promoter activation was tested by reporter assays. For human colon carcinomas, S100A4 expression, beta-catenin genotype, and metachronous metastasis were correlated. RESULTS: We identified S100A4 as the most regulated gene by gain-of-function beta-catenin using a 10K microarray. Cell lines with gain-of-function beta-catenin expressed up to 60-fold elevated S100A4 levels, displayed strongly increased migration and invasion in vitro, and induced metastasis in mice. S100A4 small interfering RNA, beta-catenin small interfering RNA, or dominant negative T-cell factor (TCF) knocked down S100A4 and blocked biological effects. S100A4 complementary DNA transfection increased migration and invasion. We identified a TCF binding site within the S100A4 promoter and demonstrated the direct binding of heterodimeric beta-catenin/TCF complexes. Reporter assays confirmed the beta-catenin-induced S100A4 promoter activity. Furthermore, S100A4 mRNA expression was increased in primary colon cancers, which later developed distant metastases, compared to non-metastasizing tumors. Colon tumors heterozygous for gain-of-function beta-catenin showed concomitant nuclear beta-catenin localization, high S100A4 expression, and metastases. CONCLUSIONS: S100A4 is a direct beta-catenin/TCF target, induces migration and invasion in vitro and metastasis in vivo, and has value for prognosis of metastasis formation in colon cancer patients.

Cell Movement↗

Cyclin-dependent kinase 2 functions in normal DNA repair and is a therapeutic target in BRCA1-deficient cancers.

Abnormal regulation of progression from G(1) to S phase of the cell cycle by altered activity of cyclin-dependent kinases (CDKs) is a hallmark of cancer. However, inhibition of CDKs, particularly CDK2, has not shown selective activity against most cancer cells because the kinase seems to be redundant in control of cell cycle progression. Here, we show a novel role in the DNA damage response and application of CDK inhibitors in checkpoint-deficient cells. CDK2(-/-) mouse fibroblasts and small interfering RNA--mediated or small-molecule--mediated CDK2 inhibition in MCF7 or U2OS cells lead to delayed damage signaling through Chk1, p53, and Rad51. This coincided with reduced DNA repair using the single-cell comet assay and defects observed in both homologous recombination and nonhomologous end-joining in cell-based assays. Furthermore, tumor cells lacking cancer predisposition genes BRCA1 or ATM are 2- to 4-fold more sensitive to CDK inhibitors. These data suggest that inhibitors of CDK2 can be applied to selectively enhance responses of cancer cells to DNA-damaging agents, such as cytotoxic chemotherapy and radiotherapy. Moreover, inhibitors of CDKs may be useful therapeutics in cancers with defects in DNA repair, such as mutations in the familial breast cancer gene BRCA1.

Animals↗

A novel repeat-associated small interfering RNA-mediated silencing pathway downregulates complementary sense gypsy transcripts in somatic cells of the Drosophila ovary.

Replication of the gypsy endogenous retrovirus involves contamination of the female germ line by adjacent somatic tissues. This is prevented by flam, an as-yet-uncloned heterochromatic pericentromeric locus, at the level of transcript accumulation in these somatic ovarian tissues. We tested the effect of a presumptive RNA silencing mechanism on the accumulation of RNAs produced by constructs containing various gypsy sequences and report that the efficiency of silencing is indeed correlated with the amount of complementary RNAs, 25 to 30 nucleotides in length, in the ovary. For instance, while these RNAs were found to display a three- to fivefold excess of the antisense strands, only the transcripts that contain the complementary sense gypsy sequences could be repressed, indicating that they are targeted at the RNA, not DNA, level. Their size and asymmetry in strand polarity are typical of the novel repeat-associated small interfering RNA (rasiRNA)-mediated pathway, recently suspected to prevent the deleterious expression of selfish DNA specifically in the germ line. Unlike microRNAs (but like rasiRNAs and, surprisingly, siRNAs as well), gypsy rasiRNAs are modified at the 3' end. The rasiRNA-associated protein Piwi (but not Aub) is required for gypsy silencing, whereas Dicer-2 (which makes siRNAs) is not. In contrast, piwi, aub, and flam do not appear to affect somatic siRNA-mediated silencing. The amount of gypsy rasiRNAs is genetically determined by the flam locus in a provirus copy number-independent manner and is triggered in the somatic tissues by some pericentromeric provirus(es), which are thereby able to protect the germ line from retroviral invasion.

3' Flanking Region↗

Small interfering RNA-mediated inhibition of hepatitis G virus gene expression in human hepatoma cell Huh-7.

The RNA interference (RNAi) phenomenon is a recently observed process in which the introduction of a double-stranded, small interfering RNA (siRNA) into a cell causes the specific degradation of a homologous single-stranded RNA. It represents an exciting new technology that could have therapeutic applications for the treatment of viral infections. Since hepatitis G virus (HGV) genome is a positive-sense single-stranded RNA, the replication of HGV does not lead to an integrated DNA genome, suggesting a particularly attractive target for RNAi study that could eliminate viral RNA from infected cells. The eukaryotic expression vector pVAX.EH containing the cDNA sequences of the entire HGV structural genes and hygromycin resistance gene downstream from the encephalomyocarditis virus (ECMV) internal ribosome entry site (IRES) was constructed and transfected into human hepatoma cell Huh-7. The modified cleavage products of the structural proteins of HGV expressed in hygromycin-resistant cell line Huh-7-EH were confirmed by RT-PCR and Western blot methods. Two specific HGV E2 siRNAs (1-E2 siRNA, 2-E2 siRNA) synthesized with T7 RNA polymerase by transcription in vitro were transfected into the Huh-7-EH cells. With the analyses of Western blot and the formation of hygromycin-resistant colonies, the inhibitions of expression of HGV structural protein by two HGV E2 siRNAs were detected and found lasting at least one week. The inhibition of 2-E2 siRNA was stronger and only 1% of the cells treated with 2-E2 siRNA formed hygromycin-resistant colonies. These results support that specific HGV 2-E2 siRNAs mediate the degradation of mRNA spanning from HGV structural gene cDNA to hygromycin resistance gene in a majority of cells. In conclusion, the Huh-7-EH cells expressing HGV structural proteins stably can be used as a cell model for studying the replication of HGV and RNAi and the enlargement of RNAi may exist, in mammalian cells.

Antiviral Agents↗

The orphan nuclear receptor, NOR-1, is a target of beta-adrenergic signaling in skeletal muscle.

beta-Adrenergic receptor (beta-AR) agonists induce Nur77 mRNA expression in the C2C12 skeletal muscle cell culture model and elicit skeletal muscle hypertrophy. We previously demonstrated that Nur77 (NR4A1) is involved in lipolysis and gene expression associated with the regulation of lipid homeostasis. Subsequently it was demonstrated by another group that beta-AR agonists and cold exposure-induced Nur77 expression in brown adipocytes and brown adipose tissue, respectively. Moreover, NOR-1 (NR4A3) was hyperinduced by cold exposure in the nur77(-/-) animal model. These studies underscored the importance of understanding the role of NOR-1 in skeletal muscle. In this context we observed 30-480 min of beta-AR agonist treatment significantly and transiently increased expression of the orphan nuclear receptor NOR-1 in both mouse skeletal muscle tissue (plantaris) and C2C12 skeletal muscle cells. Specific beta(2)- and beta(3)-AR agonists had similar effects as the pan-agonist and were blocked by the beta-AR antagonist propranolol. Moreover, in agreement with these observations, isoprenaline also significantly increased the activity of the NOR-1 promoter. Stable exogenous expression of a NOR-1 small interfering RNA (but not the negative control small interfering RNA) in skeletal muscle cells significantly repressed endogenous NOR-1 mRNA expression and led to changes in the expression of genes involved in the control of lipid use and muscle mass underscored by a dramatic increase in myostatin mRNA expression. Concordantly the myostatin promoter was repressed by NOR-1 expression. In conclusion, NOR-1 is highly responsive to beta-adrenergic signaling and regulates the expression of genes controlling fatty acid use and muscle mass.

Animals↗

siRNA and miRNA: an insight into RISCs.

Two classes of short RNA molecule, small interfering RNA (siRNA) and microRNA (miRNA), have been identified as sequence-specific posttranscriptional regulators of gene expression. siRNA and miRNA are incorporated into related RNA-induced silencing complexes (RISCs), termed siRISC and miRISC, respectively. The current model argues that siRISC and miRISC are functionally interchangeable and target specific mRNAs for cleavage or translational repression, depending on the extent of sequence complementarity between the small RNA and its target. Emerging evidence indicates, however, that siRISC and miRISC are distinct complexes that regulate mRNA stability and translation. The assembly of RISCs can be traced from the biogenesis of the small RNA molecules and the recruitment of these RNAs by the RISC loading complex (RLC) to the transition of the RLC into the active RISC. Target recognition by the RISC can then take place through different interacting modes.

Animals↗

Small interfering RNA-mediated gene silencing in T lymphocytes.

Introduction of small interfering RNAs (siRNAs) into a cell can cause a specific interference of gene expression known as RNA interference (RNAi). However, RNAi activity in lymphocytes and in normal primary mammalian cells has not been thoroughly demonstrated. In this report, we show that siRNAs complementary to CD4 and CD8alpha specifically reduce surface expression of these coreceptors and their respective mRNA in a thymoma cell line model. We show that RNAi activity is only caused by a subset of siRNAs complementary to the mRNA target and that ineffective siRNAs can compete with effective siRNAs. Using primary differentiated T lymphocytes, we provide the first evidence of siRNA-mediated RNAi gene silencing in normal nontransformed somatic mammalian lymphocytes.

Animals↗

R2D2, a bridge between the initiation and effector steps of the Drosophila RNAi pathway.

The RNA interference (RNAi) pathway is initiated by processing long double-stranded RNA into small interfering RNA (siRNA). The siRNA-generating enzyme was purified from Drosophila S2cells and consists of two stoichiometric subunits: Dicer-2(DCR-2) and a previously unknown protein that we named R2D2. R2D2 is homologous to the Caenorhabditis elegans RNAi protein RDE-4. Association with R2D2 does not affect the enzymatic activity of DCR-2. Rather, the DCR-2/R2D2 complex, but not DCR-2 alone, binds to siRNA and enhances sequence-specific messenger RNA degradation mediated by the RNA-initiated silencing complex (RISC). These results indicate that R2D2 bridges the initiation and effector steps of the Drosophila RNAi pathway by facilitating siRNA passage from Dicer to RISC.

Amino Acid Sequence↗

Small interfering RNA-mediated functional silencing of vasopressin V2 receptors in the mouse kidney.

The antidiuretic effects of arginine vasopressin (AVP) on the kidney are mediated by V2 subtype AVP receptors (V2R). To investigate the role of regulation of V2R in water and sodium homeostasis, we have developed a method for small interfering RNA (siRNA)-mediated inhibition of V2R expression in vivo. Three 21-nt siRNA sequences were chosen that specifically targeted the mouse V2R but shared no appreciable sequence homology to any other known mouse genes, including the vasopressin V1a and V1b receptors. Additionally, an siRNA sequence that shared no significant matches to any known mammalian gene sequences was chosen for use as a control. Chemically synthesized siRNA was complexed with the liposomal transfection reagent DOTAP. Each mouse (male C57BL/6) received 3.6 nmol (approximately 50 microg) of either the control (nonsilencing) or one of the V2R-targeting siRNAs via intravenous injection. Forty-eight hours after injection membranes were prepared from the inner medulla of the kidneys, and V2R expression was measured by a radioligand binding assay and Western immunoblotting. Treatment with one of the V2R-targeting siRNAs (R2) caused a 39.7 +/- 8.7% reduction in V2R-specific binding compared with the control (n = 11, P < 0.05) and a 37.0 +/- 2.3% reduction in V2R protein expression as measured by Western immunoblotting (n = 4, P < 0.001). Additionally, real-time PCR revealed that R2 siRNA treatment induced a 68.8 +/- 2.2% reduction in V2R mRNA. However, this siRNA treatment did not alter the animals' basal urine concentrating capacity under unstimulated conditions. In subsequent experiments, treatment with R2 siRNA was found to significantly attenuate the antidiuretic effects the V2R-specific AVP agonist 1-desamino-[8-D-arginine]vasopressin (dDAVP). Mice were infused with dDAVP (0.25 ng/h) for 3 days to produce maximal antidiuresis and then were injected with either the R2 siRNA or the nonsilencing control. On day 2 after treatment, urine osmolality was significantly decreased from 3,455 +/- 72 in control animals (n = 12) to 3,155 +/- 129 mosmol/kgH2O in R2 siRNA-treated animals (n = 12) (P < 0.05); similarly, on day 2 24-h urine volume was significantly increased from 0.86 +/- 0.07 ml/day to 1.11 +/- 0.06 ml/day in R2 siRNA-treated animals (P < 0.05). In summary we have demonstrated that RNA interference methodology can be used successfully in vivo to significantly reduce functional expression of the V2R in the mouse kidney.

Animals↗