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Puriney's Notes

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【bio】Nature提供RNAi科学视频详解(中英双语)  

2011-12-16 23:47:47|  分类: Bio |  标签: |举报 |字号 订阅

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Scientists've been making rapid progress in understanding RNA interference, or RNAi. Many organisms are using RNAi to control genes and it can also be used as a tool in laboratory, and in future perhaps as a therapy. 
关于对RNA干扰,即RNAi,的认知越来越增多。很多生物都借助RNAi的方式来控制基因,当然,在实验室RNAi被当作一种实验工具,在未来或许还会有RNAi医疗。

This animation will introduce you to the principles of RNAi involving two important types of RNA molecule, small interfering RNAs (siRNAs) and microRNAs (miRNAs). 
本影片将会介绍RNAi涉及到的两种小RNA分子,小干扰RNA以及小RNA。

Eukaryote cells have many sophisticated ways controlling gene expressions. In the complex environment of cell, these mechanisms need to be precisely targeted. As a group of mechanisms that use small RNA molecules to direct gene silencing, this is called RNAi. 
真核生物为控制基因表达有着非常复杂的调控体系。在复杂的细胞中,这些过程都需要精确地调控。借助小RNA来实现基因沉默,就是RNAi。

Inside the nucleus most genes that are encoded proteins are transcribed by RNA Polymerase II. The primary RNA transcript is processed by splicing and forms mature messenger RNA, sometimes called mRNA. The messenger RNA is then exported from nucleus into cytoplasm. Here ribosomes catylize the translation of messenger RNA to form polypetide chains that fold into proteins. 
负责编码蛋白的各类基因,其实是RNA聚合酶II在细胞核内的转录产物。最初的RNA转录本经过RNA剪切之后形成成熟的信使RNA,即mRNA。 信使RNA再从核内转移到胞质中去。核糖体则负责催化信使RNA发生翻译,形成多肽链进而折叠成蛋白质。

But this is also where some small RNA molecules can have their silencing effects. There are several types of regulatory small RNA. 
而也正是此时,小RNA可以发挥其沉默基因的作用。有几种具备调节功能的小RNA。 

Small interfering RNAs, known as siRNAs, are derived from longer double strand RNA that are derived produced in the cell itself, or are delivered into cell environmentally. The introduction of siRNAs, or double strand RNA, is widely used to manipulate gene expression. 
小干扰RNA,即siRNA,起源于更长的双链RNA。双链RNA可以是细胞内部自己形成的,也可以是外源导入的。外源导入siRNA常常是调控基因表达的有力工具。

microRNAs are another type of small RNA. Most microRNAs comes from RNA that are transcribed in their nucleus, which then fold and being processed before being exported into cytoplasm as double strand precursor microRNAs. 
小RNA是另外一种RNA。RNA经过转录、折叠、呈递之后转运到胞质中,形成双链的前体小RNA,最后形成成熟的小RNA(即microRNA)。

The double strand precursors of microRNAs and siRNAs bind to DICER which is an endonulease protein that cut RNAs into short segments. Most siRNAs and miRNAs are approximately 21 nucleotides long. 
小RNA和小干扰RNA的双链前体RNA会结合一种名叫DICER的内切酶。DICER会把RNA切断为小片段。通常siRNA和miRNA大约是21nt

The short double strand RNA then binds Argonaut protein. One strand of RNA is selected and remains bound to Argonauts. This is called the guide strand. The combination of RNA and Argonaut, along with other proteins, is called RNA Induced Silencing Complex, or RISC. 
被切断后的双链RNA会与Argonaut蛋白结合(简写为Ago)。最后只有一条RNA链幸存与Ago结合,而这条被选择的链称作引导链。RNA、Ago蛋白以及其他调控蛋白的复合物,称为RNA诱导沉默复合物,即RISC。 

siRNAs direct RISC to bind with specific messenger RNA. Targeting is precise, because it's determined by base paring between the siRNA and the target messenger RNA. siRNA often have perfect complementarity to their target sites. Once bound, Argonaut catalyzes the cleavage of messenger RNA, which will be then degraded. 
siRNA会引导RISC特异地绑定特定的mRNA。因为siRNA和mRNA之间的配对是严格按照碱基互补配对原则而确定的,所以siRNA介导的绑定是严格的。siRNA与相对应的mRNA有着完美的互补配对关系。一旦绑定,Argo蛋白即可促发mRNA的剪切进而导致mRNA被讲解,从而达到基因沉默的目的。

microRNAs also guide RISC to messenger RNAs. Usually only part of microRNA, known as seed, pairs with the target messenger RNA. This imprecise matching allows microRNAs to targets hundreds of endogenous messenger RNAs. Targeting by a microRNA can lead to messenger RNAs being degraded or translation being inhibited. 
microRNA也会指导RISC与mRNA绑定。但是只有一部分microRNA与目标mRNA存在互补配对关系。 这样不完全配对使得microRNA可以与上百种mRNA结合。microRNA靶定会导致mRNA的降解或者翻译抑制。

Argonauts and other small regulatory RNA co-factors are found in plants, animals, fungi, and some bacteria. They are important and multitude in biological processes, and as tools continue to be reviewed. 
Argo蛋白和其他调控RNA辅助因子,在动植物、真菌、细菌里皆有发现。他们功能重要,在各类生物过程中屡见不鲜,而且还可以作为工具,一直将会是津津乐道的话题。


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