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[求助]
求大神帮个忙，四级没过孩子，老板要翻译文献（还不是我方向的）。苦逼。。。
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siRNAs: GENOMIC DEFENDERS RNA silencing via siRNAs is thought to have originated as a system by which cells protect themselves against the actions of molecular pathogens, including viruses and transposable elements. Silencing phenomena were recognized in plants in the 1980s during investigations of viral resistance and early studies of transgenic plants. In parallel, similar phenomena were identified in the nematode Caenorhabditis elegans. (The gradual enlightenment of the scientific community to the meaning of these studies is vividly described by Matzke and Matzke [2004].) siRNAs are produced from long dsRNA molecules, which can be produced via the replication of two overlapping genes, a viral genome, or an intermediate in viral replication , or they can be the product of an RdRP. Whatever their origin, dsRNAs are perceived by the cell as unwanted and so are rapidly cleaved by DCL RNases into siRNAs (usually 21 or 24 nucleotides in length). The siRNAs bind to AGO and can cleave or interfere with translation of complementary sequences (posttranscriptional gene silencing) or interfere with transcription of a cognate DNA sequence (tran-scriptional gene silencing). When the long RNA has a viral origin, this process is often called viral-induced gene silencing. VIRAL-INDUCED GENE SILENCING Plants, like animals, are susceptible to infections by viruses. Unlike some animals, plants do not produce antibodies to defend against viral infections. Nevertheles s, like those of us with antibody-based immunity, plants can recover from an infection and acquire a specific resistance to subsequent infection by the same or a closely related virus. Viral resistance can be systemic, meaning that uninfected tissues acquire immunity to the virus, and suggesting that some sort of signal is produced that moves throughout the plant. Plant viral immunity can be conferred by the introduction of viral genes into the plant and requires either transcription of a viral gene or viral replication via an RNA intermediate. In 1999, Hamilton and Baulcombe proposed that viral RNAs are copied into antisense RNAs, which form the basis of viral resistance, and they identified short antisense RNAs correlated with gene silencing. We now know that dsRNAs are processed by DCL into siRNAs, which then target AGO proteins to the virus or related sequence. In some cases, a dsRNA viral replication intermediate is the template for DCL cleavage, but DCL also apparently recognizes and processes hairpin-like structures formed by some viral single-stranded RNA. Mutant plants that are unable to produce siRNAs are more susceptible to viral disease. Systemic viral resistance is also mediated by siRNA-based silencing, which spreads outwards to the uninfected parts of the plant from the site of infection. The signal sprea ds locally through the plasmodesmata (cytoplasmic connections between plant cells) and more widely through the phloem. Systemic resistance requires that the primary signal is amplified by host cell RdRPs. The systemic signal has long been suspected to be siRNA, and in 2010, two groups showed that small RNAs can move systemically through the plant and are necessary and sufficient for systemic silencing. The most recent data suggest that the siRNA moves systemically as a short RNA duplex. In a typical host-pathogen arms race, most viruses encode suppressors of the host cell’s RNA silencing pathways; virus strains in which the suppressors have been experimentally eliminated are significantly less pathogeni c. Targets of viral suppressors include DCLs, RdRPs, and AGOs. Recently, siRNAs were recognized as suppressors of bacterial pathogens as well, indicating that siRNA silencing is an integral and essential component of the plant’s defensive arsenal. It is interesting to note that most components of the small RNA silencing pathway are amplified through gene duplication in plants compared with other eukaryotes and that this amplifica-tion has conferred greater reliability (through redundancy) and greater diversity in pathogen silencing. |
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【答案】应助回帖
★ ★ ★ ★ ★ ★
爱与雨下: 金币+1 2013-06-21 18:45:24
peaceqing(phu_grassman代发): 金币+5, 翻译EPI+1, thanks 2013-11-07 10:31:17
爱与雨下: 金币+1 2013-06-21 18:45:24
peaceqing(phu_grassman代发): 金币+5, 翻译EPI+1, thanks 2013-11-07 10:31:17
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siRNA:遗传防御 通过siRNA介导的RNA沉默，被认为是通过细胞自我防御外界的病原分子，包括病毒和转座子。沉默现象是在1980s对转基因植物的病毒防御机制研究中发现的。 类似的沉默现在后来也在秀丽隐杆线虫中发现。（这些发现被 Matzke 和 Matzke在2004年生动地描述过。 ） siRNA由长的dsRNA(就是双链RNA，RNA一般情况下是单链的，即ssRNA)产生，在两个重叠基因的复制过程中会生成，或者是通过病毒基因组、病毒增殖的中间分子介导而生成，或者是通过RdRP（RNA-dependent RNA polymerase,就是RNA聚合酶）产生。无论是通过什么途径生成的，dsRNA都是被细胞不情愿地识别，然后迅速地被DCL RNases（Dicer-like 酶）降解成siRNA（通常长度为21-24bp）。 小师弟，你自己翻译一遍，我来润色，锻炼了你，也节省了我的时间，你觉得可好？ |
2楼2013-06-21 18:09:15
3楼2013-06-21 18:10:38
【答案】应助回帖
★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★
peaceqing(phu_grassman代发): 金币+15, good job 2013-11-07 10:31:31
peaceqing(phu_grassman代发): 金币+15, good job 2013-11-07 10:31:31
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siRNA：基因组卫士 RNA沉默的siRNA被认为是作为系统的细胞保护自己免受病原体的分子的行动，包括病毒和转座子。沉默现象是植物中公认的世纪80年代早期的病毒抗性的转基因植物的研究调查。同时，类似的现象在秀丽隐杆线虫鉴定。（科学界的渐进启示的意义这些研究是由马茨和马茨[ 2004 ]进行了生动的描述。）从长dsRNA siRNA分子产生，它可以通过两个重叠的基因复制产生，病毒基因组，或中间在病毒复制，或者他们可以RdRp的产品。不论其来源，双链RNA被认为以细胞为不必要的和正在迅速被DCL切割成siRNAs核糖核酸酶（通常21或24个核苷酸的长度）。siRNA绑定到前，可以切割或干扰的互补序列的翻译（转录后基因沉默）或干扰的同源DNA序列的转录因子（转录基因沉默）。当长的RNA病毒的起源，这个过程通常被称为病毒诱导的基因沉默。 病毒诱导的基因沉默植物，像动物一样，是由病毒感染易感。不像一些动物，植物不产生抗体来抵御病毒感染。尽管如此，像我们这些抗体为基础的免疫，植物可以从感染中恢复过来，以相同或密切相关的病毒获得后续感染的特异性抵抗。病毒抗性是全身性的，这意味着未受感染的组织中获得对病毒的免疫力，并暗示某种信号的产生，将整个工厂。植物病毒的免疫力，可由病毒基因导入植物赋予和需要的病毒基因或病毒的复制或转录通过RNA中间体。1999，汉密尔顿和鲍尔库姆提出病毒RNA复制到反义RNA，形成病毒耐药的基础，他们确定的短反义RNA基因沉默相关。我们现在知道，双链RNA由DCL为siRNA处理，然后目标前蛋白对病毒或相关序列。在某些情况下，一个dsRNA病毒复制中间体DCL切割模板，但是DCL显然也识别和处理的发夹样结构的一些病毒单链RNA形成。突变体是无法产生的siRNA更易感染病毒病。 全身性病毒性也介导的siRNA的沉默，而向外传播到植物的未受感染的部位感染的部位。信号将DS局部通过胞间连丝（细胞质之间的连接植物细胞）和通过韧皮部更广泛。全身性需要的主要信号是由宿主细胞的RNA依赖的RNA扩增。系统的信号被怀疑是siRNA，和2010，两组结果表明小RNAs可以系统地通过植物是必要的和足够的系统性沉默。最近的数据表明，siRNA的移动系统的短RNA双链。在一个典型的病原体宿主的军备竞赛，大多数病毒编码的RNA沉默途径抑制宿主细胞的病毒株的抑制；在实验已消除了显着减少致病的病毒抑制C.目标包括DCLS，程式，和前。最近，siRNA公认的细菌病原体以及抑制，表明siRNA沉默是不可或缺的植物的防御武器库组件。它是注意，小RNA沉默途径的大多数组件是通过基因复制在植物与其他真核生物，这扩大倍数赋予了更高的可靠性比较有趣的（冗余）和扩增更大的多样性病原体的沉默。 |
4楼2013-06-25 13:01:58
