中华蜜蜂气味受体基因AcerOr1 RNA最佳干扰片段的筛选

为了更好地筛选出中华蜜蜂气味受体基因AcerOr1有效干扰序列,本研究以中华蜜蜂气味受体基因AcerOr1为靶标,分别选取3个片段AcerOr1-1（429 bp）、AcerOr1-2（218 bp）和AcerOr1-3（543 bp）,并构建相应的dsRNA表达载体,获取dsRNA后通过单只饲喂进行体内RNAi实验,运用qPCR和Western从mRNA水平和蛋白水平检测干扰效率。实验结果显示：片段大小429 bp组dsAcerOr1-1和对照组mRNA表达量之间不具有显著的统计学差异（P＞0.05）,片段大小为218 bp的dsAcerOr1-2组和片段大小为543 bp的dsAcerOr1-3组对AcerOr1表达量都有显著的抑制（P＜0.05）,抑制率分别为88.85%±0.12%和69.16%±1.06%,以片段大小为218 bp的dsAcerOr1-2干扰效果最佳。Western blot结果显示：与mRNA表达水平检测结果一致,饲喂dsAcerOr1-1 AcerOr1蛋白的表达量与对照组差异不显著（P＞0.05）,而饲喂dsAcerOr1-2和dsAcerOr1-3后AcerOr1蛋白的表达量均受到显著抑制（P＜0.05）。本试验成功构建AcerOr1基因干扰载体,最终确定218 bp的dsAcerOr1-2为最佳干扰片段,证实其能有效抑制目的基因mRNA和蛋白的表达,为进一步研究该基因的体内外功能奠定了基础。     

RNA interference targeting alpha8 integrin attenuates smooth muscle cell growth

alpha8 integrin gene silencing has been shown to result in the stress fibre disassembly. Stress fibres are required for cell adhesion to promote passage through cell cycle. Thus, we hypothesized that alpha8 integrin gene silencing might affect vascular smooth muscle cell (VSMC) growth. Short interference RNA (siRNA) targeting alpha8 integrin in rat VSMCs resulted in reduced DNA synthesis. Moreover, siRNA-alpha8 integrin prevented thrombin-induced proliferation. RhoA plays a critical role in regulating VSMC growth. alpha8 integrin co-immunoprecipitated with RhoA and siRNA-alpha8 reduced membrane associated RhoA. Our data suggest that alpha8 integrin expression is critical for VSMC growth, which has potential implications in postangioplasty neointimal hyperplasia.     

RNA interference targeting focal adhesion kinase enhances pancreatic adenocarcinoma gemcitabine chemosensitivity

Focal adhesion kinase (FAK) is an important regulator of cellular signaling, migration, apoptosis, and cell cycle progression. We tested the hypothesis that FAK is a determinant of gemcitabine chemoresistance in pancreatic adenocarcinoma cells and examined the effect of inhibiting FAK expression on gemcitabine-induced cytotoxicity in vitro and in vivo. FAK expression was quantified by Western and Northern blots. Expression of FAK was suppressed using small interfering RNA (siRNA). Gemcitabine-induced cytotoxicity was quantified and apoptosis was characterized. Akt activity was determined by in vitro kinase assay. We assessed the therapeutic applicability of FAK siRNA in a nude mouse orthotopic xenograft model. While not affecting cellular proliferation or apoptosis in the absence of gemcitabine, FAK siRNA potentiated gemcitabine-induced cytotoxicity in vitro and in vivo. FAK siRNA treatment suppressed Akt activity, which may contribute to its chemosensitizing effect.     

RNA interference targeting CITRON can significantly inhibit the proliferation of hepatocellular carcinoma cells

CITRON (rho-interacting, serine/threonine kinase 21), which is a key component of the midbody, is essential for cytokinesis. However, the role of CITRON in hepatocellular carcinoma (HCC) is poorly understood. Here we first measured the expression of CITRON in HCC specimens by quantitative real-time RT–PCR and immunohistochemical staining. The results showed CITRON to be frequently up-regulated in HCC as compared with adjacent non-tumour tissues. Then we employed adenovirus-mediated RNA interference against CITRON to assess its anti-proliferation effect on SMMC-7721 cells, a representative HCC cell line. The resulting data demonstrated that CITRON knockdown was capable of inhibiting the proliferation and colony formation of SMMC-7721 cells, with an obvious increase of multinucleated cells. Furthermore, we subcutaneously injected the SMMC-7721 cells with the CITRON knockdown into nude mice to evaluate the tumourigenicity. The data indicated that adenovirus-mediated RNA interference can suppress tumourigenicity in vivo of HCC cells. Our data suggest that CITRON may be a potential target for therapeutic intervention in HCC.     

RNA interference targeting cathepsin B of the carcinogenic liver fluke, Opisthorchis viverrini

Functional genomics have not been reported for Opisthorchis viverrini or the related fish-borne fluke, Clonorchis sinensis. Here we describe the introduction by square wave electroporation of Cy3-labeled small RNA into adult O. viverrini worms. Adult flukes were subjected to square wave electroporation employing a single pulse for 20 ms of 125 V in the presence of 50 μg/ml of Cy3-siRNA. The parasites tolerated this manipulation and, at 24 and 48 h after electroporation, fluorescence from the Cy3-siRNA was evident throughout the parenchyma of the worms, with strong fluorescence evident in the guts and reproductive organs of the adult worms. Second, other worms were treated using the same electroporation settings with double stranded RNA targeting an endogenous papain-like cysteine protease, cathepsin B. This manipulation resulted in a significant reduction in specific mRNA levels encoding cathepsin B, and a significant reduction in cathepsin B activity against the diagnostic peptide, Z-Arg-Arg-AMC. This appears to be the first report of introduction of reporter genes into O. viverrini and the first report of experimental RNA interference (RNAi) in this fluke. The findings indicated the presence of an intact RNAi pathway in these parasites which, in turn, provides an opportunity to probe gene functions in this neglected tropical disease pathogen.     

RNA干扰

RNA干扰（RNA interference,RNAi）现象是指,当与内源性mRNA编码区某段序列同源的双链RNA(dsRNA)导入细胞后,该mRNA发生特异性的降解,而导致该基因表达的沉寂。这可能反映了生物防范病毒或转座子诱导DNA突变的一种防御机制。RNA干扰已经成为一种重要的研究基因功能的有力工具,并且有希望在对疾病的防御及治疗中发挥重要的作用。     

RNA干涉的研究进展

生物体内导入双链RNA后会引起体内同源基因特异性的沉默,这种现象称为RNA干涉,本主要介绍RNA干涉的研究历史,作用机制和应用等方面的情况。     

RNA干涉技术

RNA干涉(RNAi)技术是利用一些小的双链RNA来高效、特异地阻断体内特定基因的表达,并促使mRNA降解,从而诱使细胞表现出特定基因缺失的表型。本从RNAi技术的历史、作用机制、研究策略、研究现状及应用前景等几个方面进行了综述,预测RNAi将会给基因治疗的发展带来新的希望。     

RNA interference targeting programmed death receptor-1 improves immune functions of tumor-specific T cells

Adoptive cell transfer (ACT), either using rapidly expanded tumor infiltrating lymphocytes or T-cell receptor transduced peripheral blood lymphocytes, can be considered one of the most promising approaches in cancer immunotherapy. ACT results in the repopulation of the host with high frequencies of tumor-specific T cells; however, optimal function of these cells within the tumor micro-environment is required to reach long-term tumor clearance. We and others have shown that ongoing anti-tumor immune responses can be impaired by the expression of ligands, such as PD-L1 (B7-H1) on tumor cells. Such inhibitory molecules can affect T cells at the effector phase via their receptor PD-1. PD-L1/PD-1 interaction has indeed been shown crucial in inducing T-cell anergy and maintaining peripheral tolerance. In order to maximize anti-tumor responses, antibodies that target the PD-1/PD-L1 axis are currently in phase I/II trials. Alternatively, a more refined approach could be the selective targeting of PD-1 in tumor-specific T cells to obtain long-term resistance against PD-1-mediated inhibition. We addressed whether this goal could be achieved by means of retroviral siRNA delivery. Effective siRNA sequences resulting in the reduction of surface PD-1 expression led to improved murine as well as human T-cell immune functions in response to PD-L1 expressing melanoma cells. These data suggest that blockade of PD-1-mediated T-cell inhibition through siRNA forms a promising approach to achieve long-lasting enhancement of tumor-specific T-cell function in adoptive T-cell therapy protocols.     

Depletion of key protein components of the RISC pathway impairs pre-ribosomal RNA processing

Little is known about whether components of the RNA-induced silencing complex (RISC) mediate the biogenesis of RNAs other than miRNA. Here, we show that depletion of key proteins of the RISC pathway by antisense oligonucleotides significantly impairs pre-rRNA processing in human cells. In cells depleted of Drosha or Dicer, different precursors to 5.8S rRNA strongly accumulated, without affecting normal endonucleolytic cleavages. Moderate yet distinct processing defects were also observed in Ago2-depleted cells. Physical links between pre-rRNA and these proteins were identified by co-immunoprecipitation analyses. Interestingly, simultaneous depletion of Dicer and Drosha led to a different processing defect, causing slower production of 28S rRNA and its precursor. Both Dicer and Ago2 were detected in the nuclear fraction, and reduction of Dicer altered the structure of the nucleolus, where pre-rRNA processing occurs. Together, these results suggest that Drosha and Dicer are implicated in rRNA biogenesis.     

Cholesterol depletion induced by RNA interference targeting DHCR24 protects cells from liposome-induced cytotoxicity

Abstract

Existing evidence has demonstrated liposomes as the gene transporter induce the cytotoxicity during the transfection process through several known pathways. In the present study, we investigated the possibility of siRNAs targeting 3-β-hydroxysterol △-24-reductase (DHCR24), which encodes an enzyme catalyzing the last step of cholesterol biosynthesis, to suppress the liposome cytotoxicity induced by lipid-based transfection reagent in the neuroblastoma cell line N2A. We found that the siRNAs targeting DHCR24 mRNA protect cells from the liposome-induced cell death, probably through the effect of siDHCR24s on the reduction of the cellular cholesterol and decrease in the generation of reactive oxygen species (ROS). This suggests that siRNAs targeting DHCR24 or other methods that reduce the intracellular cholesterol levels might be a good strategy for avoiding the cytotoxicity of liposomes, without impairing its efficiency of gene-delivering.     

Autoimmune epitopes in messenger RNA

Patients with systemic autoimmune disorders produce autoantibodies against sequence-specific conformational RNA epitopes on U1 snRNA, 28S rRNA, and transfer RNAs. The molecular basis for immunological reactivity with these highly abundant and stable RNAs is not understood. Here, we report the existence of discrete RNA epitopes in messenger RNAs that are generally less abundant and less stable than snRNAs and tRNAs. An iterative selection and amplification procedure using pooled autoimmune patient sera identified immunoreactive mRNA species. Following deconvolution of the pools to identify the reactive sera, several mRNAs recognized by these autoantibodies were cloned and sequenced. Detailed analysis using one particular serum indicated reactivity against the messages encoding alternative splicing factor (ASF/SF2) and calmodulin. Deletion and site-directed mutagenesis determined that an epitope recognized by this serum is located in a 17-base stem-loop structure common to both messages. This serum was then used to immunoprecipitate native mRNAs encoding ASF/SF2 and calmodulin from total HeLa cell RNA. Our results demonstrate that despite its low abundance and instability, messenger RNA is capable of reacting with autoantibodies generated during an autoimmune response. These data are consistent with direct presentation as a model to explain the generation of RNA conformation-specific autoantibodies.     

Environmental RNA interference

The discovery of RNA interference (RNAi), the process of sequence-specific gene silencing initiated by double-stranded RNA (dsRNA), has broadened our understanding of gene regulation and has revolutionized methods for genetic analysis. A remarkable property of RNAi in the nematode Caenorhabditis elegans and in some other multicellular organisms is its systemic nature: silencing signals can cross cellular boundaries and spread between cells and tissues. Furthermore, C. elegans and some other organisms can also perform environmental RNAi: sequence-specific gene silencing in response to environmentally encountered dsRNA. This phenomenon has facilitated significant technological advances in diverse fields including functional genomics and agricultural pest control. Here, we describe the characterization and current understanding of environmental RNAi and discuss its potential applications.     

RNA干扰与技术

RNA干扰(RNA interference,RNAi)是由双链RNA诱导的、序列特异的基因沉默机制。它是自然存在于植物、线虫和果蝇中抵抗外来基因(包括病毒、转座子)入侵的方式。在哺乳动物细胞中,能够人工诱导RNA干扰,沉默有同源序列基因表达。这一新技术具有特异性、高效性。因此,正被用来研究人类基因组的功能、肿瘤和抗病毒感染等。