RNA干扰机制的研究进展

RNA干扰(RNAi)广泛存在于各种生物体中,是参与细胞防御与分化调控的重要机制之一。RNAi的作用由双链RNA启动,通过在转录、转录后和翻译等多个水平上对同源基因表达的特异阻断和抑制来实现,清晰地阐明其作用机制将为功能基因组学、发育生物学,以及抗肿瘤、抗病毒的新策略研究提供重要的理论依据。本文综述了近年来有关RNAi机制的研究进展。     

RNA干扰与基因敲除

RNAi是指通过双链RNA介导特异性降解靶mRNA,导致转录后水平基因沉默的现象。其作用途径有RdRP依赖的RNAi的途径与非RdRP依赖的RNAi途径2种。利用RNAi的基因敲除技术在dsRNA序列选择、质粒或病毒为载体的dsRNA体内合成、发夹样siRNA的转录、dsRNA的导入方法等方面取得了很大进展,在研究人类或其他生物基因组中未知基因及蛋白质的功能等领域具有诱人的应用前景。     

RNA干扰研究进展

RNA干扰(RNA interference,RNAi)是指由双链RNA(double-strandedRNA,dsRNA)启动的序列特异的转录后基因沉默现象,广泛存在于真菌、植物和动物中。它是细胞内由双链RNA诱导降解与其配对的特定mRNA的过程。细胞内双链RNA在酶的作用下,形成20-25碱基大小的小干扰RNA(siRNAs),由siRNAs进一步掺入多组分核酸酶并使其激活,从而精确降解与siRNAs序列相同的mRNA,抑制该基因在细胞内的翻译表达。RNAi技术是近年来迅速发展起来的高效、特异、易操作的基因沉默技术。与反义寡核苷酸等传统方法相比,RNAi技术有着无可比拟的优势。本文就其近年的研究进展作一综述。     

植物RNA沉默机制的研究进展

RNA沉默是真核生物中普遍存在的抵抗病毒复制表达、抑制转座子转座及调控基因表达的监控机制。植物中的RNA沉默(转录水平的基因沉默PTGS)在RdRP的作用、transitive RNAi的双向延伸、沉默效应的系统性传播等方面与动物中有所不同,且植物中的内源性miRNA在数量和种类上也更具多样性。文中就以上方面及RNA沉默在植物中的应用进行了综述。     

RNA干扰技术及应用的研究进展

RNA干扰(RNAi)是由双链RNA(dsRNA)介导的序列特异的基因沉默现象,RNAi效应具有高特异性和高效性的显著特征,能够在细胞和子代间传递.除诱导同源序列mRNA降解或阻止其翻译而使目的基因表达受阻的转录后基因沉默外,RNA干扰可通过组蛋白甲基化影响染色质结构、通过DNA甲基化在转录水平调节基因表达,在翻译水平调节机体发育,并作为基因组的免疫系统,使转座因子或重复序列区域异染色质化,有效抑制了转座子和重复序列之间的同源重组对基因组可能造成的破坏,使生物基因组在长期进化过程中能保持结构的完整性和遗传的连续性. RNA干扰以阻抑基因的表达来模拟基因敲除技术,为反向遗传学研究基因功能提供了一种快速和简便的方法.RNA干扰技术日趋成熟和完善,为人们迅速准确地分析基因功能提供了极为有用的工具,同时在临床应用和治疗肿瘤和癌症等方面也有着巨大的应用前景.     

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。     

dsRNA介导的RNA干扰

在多种生物中 ,外源或内源性的双链ＲＮＡ(ｄｏｕｂｌｅ ｓｔｒａｎｄｅｄＲＮＡ ,ｄｓＲＮＡ)导入细胞中 ,与ｄｓＲＮＡ同源的ｍＲＮＡ则受到降解 ,因而其相应的基因受到抑制。这种转录后基因沉默 (ｐｏｓｔ ｔｒａｎｓｃｒｉｐｔｉｏｎａｌｇｅｎｅｓｉｌｅｎｃｉｎｇ ,ＰＴＧＳ)机制首先在线虫 (Ｃ .ｅｌｅｇａｎｓ)中得以证实。由于这是一种在ＲＮＡ水平的基因表达抑制 ,故也称为ＲＮＡ干扰 (ＲＮＡｉｎｔｅｒｆｅｒ ｅｎｃｅ) ,简称ＲＮＡｉ[1] 。随后发现 ,在各种生物 ,如果蝇[2 ] 、拟南芥菜[3 ] 、及小鼠[4] 等均存在ｄｓＲＮＡ介导…     

RNA干涉技术(RNAi)应用研究进展

RNA干涉是通过双链RNA的介导特异性地降解相应序列的mRNA,从而导致转录后水平的基因沉默,这一过程在拟南芥、线虫和真菌等多种模式植物中发现。RNAi是研究多种生物基因功能的有效手段,本文综述了RNA干涉的分子机理及其应用研究进展。     

RNA干涉的最新研究进展

RNA干涉 (RNAi)是将双链RNA(dsRNA)导入细胞引起特异基因mRNA降解的一种细胞反应过程 .它是转录后基因沉默 (PTGS)的一种 .RNAi在生物界中广泛存在 .RNAi发生过程主要分为 3个阶段 :起始阶段 ,扩增阶段 ,效应阶段 .RNAi在维持基因组稳定、保护基因组免受外源核酸侵入、基因表达调控等方面发挥重要生物学作用 .RNAi作为基因沉默的一个工具 ,已被广泛用于基因功能研究、基因治疗和新药研究与开发等方面 .     

RNA interference induced by siRNAs modified with 4'-thioribonucleosides in cultured mammalian cells

Short interfering RNAs (siRNAs) variously modified with 4'-thioribonucleosides against the Photinus luciferase gene were tested for their induction of the RNA interference (RNAi) activity in cultured NIH/3T3 cells. Results indicated that modifications at the sense-strand were well tolerated for RNAi activity except for full modification with 4'-thioribonucleosides. However, the activity of siRNAs modified at the antisense-strand was dependent on the position and the number of modifications with 4'-thioribonucleosides. Since modifications of siRNAs with 4'-thioribonucleosides were well tolerated in RNAi activity compared with that of 2'-O-methyl nucleosides, 4'-thioribonucleosides might be potentially useful in the development of novel and effective chemically modified siRNAs.     

RNA干扰机制研究进展

RNAi是多种生物体内由dsRNA介导的同源mRNA降解现象。这是一个高度特异化的过程,涉及多种蛋白质的共同参与。在这一过程中,siRNA的结构影响其两条链装配到RISC中去的能力。除了与RISC结合外,siRNA还引导了RITS复合物结合到同源染色质,介导异染色质化过程。干扰效应的扩散,即系统性沉默可能依赖于跨膜蛋白的转运,并且很可能是在多因素调控下完成的。Abstract: RNA interference (RNAi) is a phenomenon that the double-stranded RNA (dsRNA) intermediates the degradation of complementary mRNA found in many organisms. This is a specifically mechanism involved in kinds of proteins to complete the interference function. Structure of siRNA affects which strand will be assembled into RISC. Another role of siRNA is directing RITS complex to bind with homologue chromosome, and then induces heterochromatinization. Although systemic silence induced by dsRNA is observed in Caenorhabditis elegans and plants, this progress is probably transmembrane protein-dependent, and mostly, the systemic silencing is controlled by multi-factors.     

The capacity of transgenic tobacco to send a systemic RNA silencing signal depends on the nature of the inducing transgene locus

RNA silencing is a conserved eukaryotic pathway in which double-stranded RNA (dsRNA) triggers destruction of homologous target RNA via production of short-interfering RNA (siRNA). In plants, at least some cases of RNA silencing can spread systemically. The signal responsible for systemic spread is expected to include an RNA component to account for the sequence specificity of the process, and transient silencing assays have shown that the capacity for systemic silencing correlates with the accumulation of a particular class of small RNA. Here, we report the results of grafting experiments to study transmission of silencing from stably transformed tobacco lines in the presence or absence of helper component-proteinase (HC-Pro), a viral suppressor of silencing. The studied lines carry either a tail-to-tail inverted repeat, the T4-IR transgene locus, or one of two different amplicon transgene loci encoding replication-competent viral RNA. We find that the T4-IR locus, like many sense-transgene-silenced loci, can send a systemic silencing signal, and this ability is not detectably altered by HC-Pro. Paradoxically, neither amplicon locus effectively triggers systemic silencing except when suppressed for silencing by HC-Pro. In contrast to results from transient assays, these grafting experiments reveal no consistent correlation between capacity for systemic silencing and accumulation of any particular class of small RNA. In addition, although all transgenic lines used to transmit systemic silencing signals were methylated at specific sites within the transgene locus, silencing in grafted scions occurred without detectable methylation at those sites in the target locus of the scion.     

RNA Interference. An Approach to Produce Knockout Organisms and Cell Lines

In various eucaryotic organisms double-stranded RNA causes effective degradation of homologous mRNA molecules by a process called RNA interference. RNA interference is a phenomenon associated with gene suppression via regulatory RNA molecules, which are common in plants, animals, and fungi. The discovery of RNA interference stimulated the development of new approaches for suppression of target gene expression, production of stable knockout cell lines and organisms, and also stimulated studies on possible intracellular functions of this phenomenon.     

In vitro analysis of RNA interference in Drosophila melanogaster

Double-stranded RNA (dsRNA) triggers the destruction of mRNA sharing sequence with the dsRNA, a phenomenon termed RNA interference (RNAi). The dsRNA is converted by endonucleolytic cleavage into 21- to 23-nt small interfering RNAs (siRNAs), which direct a multiprotein complex, the RNA-induced silencing complex to cleave RNA complementary to the siRNA. RNAi can be recapitulated in vitro in lysates of syncytial blastoderm Drosophila embryos. These lysates reproduce all of the known steps in the RNAi pathway in flies and mammals. Here we explain how to prepare and use Drosophila embryo lysates to dissect the mechanism of RNAi.     

RNA干涉分子机制研究进展

RNA干涉（RNA interference,RNAi）是生物体内的一种通过双链RNA(dsRNA)来抵抗病毒入侵和抑制转座子活动的自然机制.双链RNA与同源mRNA互补结合而使特定基因失活,这一过程已经在包括拟南芥、线虫和真菌等多种模式生物中得到揭示.近来研究表明,21～25 nt的小干涉RNA（small interference RNA, siRNA）可介导哺乳动物细胞特异性基因沉默.RNAi具有高效性和高度特异性,可能成为关闭基因的新技术而在基因功能研究和疾病基因治疗中发挥重要作用.