Dicer蛋白在RNA干涉中的作用研究进展

近年来，对功能基因组的研究使人们对基因功能的认识不断深入。后基因时代的来临，又使基因功能研究备受瞩目。RNA干涉对基因表达的抑制为我们提供了新的研究工具。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。它是转录后基因沉寂(PTGS)的一种。本文简要介绍RNAi的发生机制及该过程中重要分子Dicer的研究进展。     

CDK2 RNA干扰后HepG2细胞蛋白表达的变化

目的 探讨稳定转染CDK2干扰RNA对人肝癌细胞株HepG2细胞生物活性及细胞核蛋白质的改变.方法 构建稳定转染pGenesil-1-CDK2的HepG2细胞系,MTT法检测细胞增殖、流式细胞术检测细胞周期的改变.通过RT-PCR和双向凝胶电泳-质谱技术-数据库搜索,比较转染前后CDK2 mRNA的表达和细胞核蛋白质的变化.并通过Western blot法对显著差异蛋白进行验证.结果 与空质粒组PHK-siRNA-HepG2细胞和未转染组HepG2细胞相比,pCDK2-siRNA-HepG2组细胞的生长速度减慢(P＜0.01),稳定转染CDK2 RNAi组细胞的CDK2 mRNA表达水平显著下降.通过双向电泳-质谱技术得到4个稳定转染CDK2 siRNA的HepG2细胞不表达的蛋白质,Westem blot法证实双向电泳结果的可信性.结论 CDK2干扰RNA可明显降低HepG2细胞CDK2 mRNA的表达,抑制HepG2细胞的增殖,干扰后的HepG2细胞不表达的蛋白质分别是类核糖体蛋白S12、β-肌动蛋白、锌指蛋白276和伴侣蛋白10相关蛋白.     

Interaction of viruses with the mammalian RNA interference pathway

It has been known for some time that plants and insects use RNA interference (RNAi) as nucleic acid-based immunity against viral infections. However, it was unknown whether mammalian cells employ the RNA interference pathway as an antiviral mechanism as well. Over the past years, it has become clear that a variety of viruses, first in plants but recently in insect and mammalian viruses as well, encode suppressors of the RNAi pathway arguing for an antiviral role of this machinery. More recent findings have revealed that certain viruses encode their own microRNAs or microRNA-like RNA molecules, which are processed by the mammalian RNAi machinery. Furthermore, host-encoded microRNAs have been shown to both silence and enhance intracellular levels of viral RNAs. These findings argue that interactions between the RNAi pathway and viral genomes can profoundly affect the outcomes of the viral life cycles and contribute to the pathogenic signatures of the infectious agents.     

RNA interference silencing of DRAL affects processing of amyloid precursor protein

In a previous study, we reported that Alzheimer's disease-associated presenilin-2 interacts with a LIM-domain protein, namely, DRAL/FHL2/SLIM3. In this study, we investigated whether DRAL modifies the metabolism of the amyloid precursor protein (APP). We used small interfering RNA (siRNA) to knockdown DRAL in COS7 and HEK293 cells that stably overexpress APP695. We found that the knockdown was accompanied by a decrease in the amount of secreted alpha-secretase-cleaved APP and the membrane-bound C-terminal fragment C83 and an increase in the amount of secreted beta-amyloid peptide (Abeta) from the cells. We also found that in addition to a disintegrin and metalloprotease (ADAM)-17, DRAL binds to ADAM-10. Thus, DRAL may be involved in the processing of APP through the alpha-secretase pathway.     

应用RNAi抑制细胞中绿色荧光蛋白的表达

目的 在293T和Mel细胞中研究RNA干扰（RNA interference，RNAi）对绿色荧光蛋白（enhanced green fluorescent protein，eGFP）表达的沉默作用。方法 以巢式PCR方法从人胚肾293T细胞中克隆出依赖于RNA聚合酶Ⅲ的H1启动子，并用于驱动RNAi片段的合成；构建能抑制eGFP特异性表达的RNAi载体（TRl）。将eGFP载体和RNAi干扰载体共转染293T和Mel两类细胞中，应用荧光显微镜观察、逆转录-PCR、荧光辅助细胞分选技术和定量逆转录-PCR方法分析上述细胞中RNAi对eGFP表达的抑制情况。结果 RNAi载体能有效地使293T和Mel细胞中红系特异的eGFP表达量均降低约50％以上。结论 本文构建的RNAi载体能有效的抑制目的基因eGFP在细胞中的表达。     

Trapping of messenger RNA by Fragile X Mental Retardation protein into cytoplasmic granules induces translation repression

Absence of Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein, is responsible for the Fragile X syndrome, the most common form of inherited mental retardation. FMRP is a cytoplasmic protein associated with mRNP complexes containing poly(A)+mRNA. As a step towards understanding FMRP function(s), we have established the immortal STEK Fmr1 KO cell line and showed by transfection assays with FMR1-expressing vectors that newly synthesized FMRP accumulates into cytoplasmic granules. These structures contain mRNAs and several other RNA-binding proteins. The formation of these cytoplasmic granules is dependent on determinants located in the RGG domain. We also provide evidence that FMRP acts as a translation repressor following co-transfection with reporter genes. The FMRP-containing mRNPs are dynamic structures that oscillate between polyribosomes and cytoplasmic granules reminiscent of the Stress Granules that contain repressed mRNAs. We speculate that, in neurons, FMRP plays a role as a mRNA repressor in incompetent mRNP granules that have to be translocated from the cell body to distal locations such as dendritic spines and synaptosomes.     

Delivering RNA interference to the mammalian brain

RNA interference (RNAi) is a new modality in gene therapy which can elicit down-regulation of gene expression and has enormous potential in the treatment of neurological diseases. RNAi is a conserved system through which double stranded RNA (dsRNA) guides sequence specific mRNA degradation. The RNAi apparatus may be artificially triggered by delivery of naked siRNA molecules or by plasmid-based expression of dsRNA. Before these techniques can be used as effective treatments in the brain, efficient methods of in vivo delivery must be devised. This review first describes the mechanism of RNAi, and then critically examines both viral and non-viral methods for delivery of RNAi to the mammalian brain. There have been a number of important recent publications in this field and the progress towards effective in vivo delivery of RNAi to the central nervous system is discussed. Finally, potential problems that must be considered before applying this technology to the human brain are outlined.     

RNA interference in functional genomics and medicine

RNA interference (RNAi) is the sequence-specific gene silencing induced by double-stranded RNA (dsRNA). Being a highly specific and efficient knockdown technique, RNAi not only provides a powerful tool for functional genomics but also holds a promise for gene therapy. The key player in RNAi is small RNA (approximately 22-nt) termed siRNA. Small RNAs are involved not only in RNAi but also in basic cellular processes, such as developmental control and heterochromatin formation. The interesting biology as well as the remarkable technical value has been drawing widespread attention to this exciting new field.     

RNA干扰分子机制研究进展

RNA干扰 (RNA interference,RNAi)即双链 RNA(double- stranded RNA,ds RNA)介导的同源m RNA特异性降解过程。作为一种简单有效的影响基因表达和一定程度上替代基因敲除的遗传学工具 ,RNAi已在秀丽新小杆线虫、黑腹果蝇、拟南芥、红色面包霉菌等多种模式生物体中得到广泛证实。同时 ,RNAi的分子机制的研究也不断取得进展 ,包括对基因转录后水平、翻译水平、基因组甲基化及沉默信号的传递等层次的研究。清晰地阐明 RNAi作用机理 ,将为大规模的基因系统筛查、新基因的发现、人类肿瘤及难治性疾病的基因治疗提供重要的理论依据和有力的工具。     

RNAi抑制乳腺癌MCF-7/ADR细胞乳腺癌耐药蛋白基因研究

目的 利用RNAi技术干扰耐药乳腺癌细胞MCF-7/ADR的BCRP(乳腺癌耐药蛋白)基因的表达,观察MCF-7/ADR细胞BCRP的mRNA变化,BCRP蛋白的表达以及对阿霉素耐药性的变化.方法 设计3条不同(BCRPl, BCRP2, BCRP4)的RNA干扰链,构建出pGenesil-BCRP-EGFP(绿色荧光蛋白)质粒,设立对照组,空白质粒(HK)组及RNAi干扰组进行实验.半定量RT-PCR检测不同组的BCRP的mRNA水平,Westem-blot检测不同组的BCRP蛋白的水平,MTT法分析RNAi干扰组药敏性变化.结果 RT-PCR和Westem-blot检测结果显示:BCRP的mRNA和蛋白的表达受抑制,以BCRP1组干扰效果明显,明显弱于其他组.MTT比色法结果显示:BCRP1组对阿霉素的药物敏感性明显提高,与对照组差异有显著性(P<0.05).结论 RNAi能抑制BCRP基因转录和翻译水平的表达,其中以BCRP1的干扰效果明显,能明显提高MCF-7/ADR对阿霉素的药物敏感性.     

RNA干扰技术应用的新进展

RNA干扰(RNAinterferenceRNAi)技术是一种发展快并有应用前景的基因控制技术,它能特异地沉默内源或外源性靶基因,目前已应用于多学科的研究。RNAi技术在多种生物体的研究中都可应用,包括植物、真菌、病毒、哺乳类动物等。这项新技术在医学领域的应用尤为突出,不仅可应用于基础研究,还有望成为攻克肿瘤、艾滋病、遗传性疾病等的新的克星,尤其siRNA在治疗疾病方面将有更广阔的前景。RNAi是近10年来分子生物学领域最热门的研究方向之一。     

Single nucleotide polymorphisms in antigen processing machinery component ERAP1 significantly associate with clinical outcome in cervical carcinoma

Genetic variation of the antigen processing machinery (APM) components TAP2, LMP7, and ERAP1 is related to cervical carcinoma risk, although the relation with expression and clinical outcome remains unknown. We have investigated the occurrence of APM component single nucleotide polymorphisms (SNPs) in cervical carcinoma. Twelve nonsynonymous, coding SNPs in the TAP1, TAP2, LMP2, LMP7, and ERAP1 genes were genotyped in 75 cervical carcinoma patients with known APM component and HLA class I expression levels. Individual genotype distributions were assessed for association with APM component expression, various histopathological parameters and survival. Genotype distributions at the ERAP1‐56 and ERAP1‐127 loci were significantly associated with overall survival (OS); haplotype construction spanning these two SNPs revealed that the combination of a major allele at ERAP1‐56 and a minor allele at ERAP1‐127 was significantly associated with survival, homozygosity for this haplotype being associated with decreased OS (5‐year survival 50% vs. 70 and 81% for complete absence or heterozygosity for this haplotype, respectively; P = 0.021). Heterozygosity for this haplotype was an independent predictor for better OS in multivariate analysis (HR = 0.219; P = 0.014). These data indicate that genetic variation in APM component genes, particularly ERAP1, is an important contributing factor in cervical carcinogenesis, progressive tumor growth and survival. The location of the ERAP1‐127 SNP in the peptidase M1 domain of the ERAP1 aminopeptidase suggests the possibility of direct functional consequences of variation at this locus. © 2009 Wiley‐Liss, Inc.