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本帖最后由 生命的流浪者 于 2011-10-26 10:49 编辑 ! |, E4 z" U1 W1 t5 E. a
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生物体的生殖系细胞担负着遗传信息的世代传递，其基因组的完整性对于个体和物种维持都至关重要。而基因组中大量存在的转座子等DNA移动元件则有可能引发基因组突变。科学家们在研究中证实生物体通常会利用一些小RNA分子引导蛋白质去沉默基因组中的转座子。这些信号通路普遍存在于原核细胞和真核细胞中，并在物种间以保守的机制发挥作用，其中包括识别外源遗传元件，激活沉默反应，维持活性转座子事件“记忆”等。而与这些Piwi蛋白相关的小RNA（称作pi RNAs）在这些过程中发挥了关键性的作用。
0 K$ U+ R) b2 g3 v2007年，Brennecke等提出piRNA信号可能是作为一个分子适应性免疫系统，感知并对抗沉默外来入侵遗传元件功能。（http://www.ebiotrade.com/）
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http://www.cell.com/COLLECTIONS-RNA-Genome-Stability
# ~) p. x g0 l9 gCells must control transposons and foreign genetic elements to maintain genomic stability. This is especially important in gametes, where unchecked transposon activity could affect the next generation. We now know that organisms have pathways in which small RNAs guide proteins to actively silence transposons in the genome. These pathways exist in prokaryotes and eukaryotes, with general mechanisms conserved between the two groups. These include mechanisms for recognizing foreign genetic elements, activating the silencing responses, and maintaining a "memory" of the active transposon event. Small RNAs associated with piwi proteins — known as piRNAs — are critical to these processes. " }+ g5 \3 d$ X0 e
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In 2007, Brennecke et al. proposed that the piRNA pathway could act as a molecular adaptive immune system, capable of sensing and reacting to adaptive transposons by silencing them. We begin this Collection looking back at these findings and then taking a broader view to appreciate how much we have learned about the roles of small RNAs in the maintenance of genomic stability. " R3 L# u3 @7 Y4 N u8 O* T, _
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Discrete Small RNA-Generating Loci as Master Regulators of Transposon Activity in Drosophila. ' o* M/ D) b- Y8 {: s( @
Julius Brennecke, Alexei A. Aravin, Alexander Stark, Monica Dus, Manolis Kellis, Ravi Sachidanandam, Gregory J. Hannon 0 y; t. `2 W" M- f- s
# H% X d. g7 m: d7 M; z: eSnapShot: Mouse piRNAs, PIWI Proteins, and the Ping-Pong Cycle
# m" }9 P) D/ ~5 k5 n# WJogender S. Tushir, Phillip D. Zamore, Zhao Zhang |
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发表于 2011-10-26 10:47
