Silencing-associated and meiosis-specific small RNA pathways in Paramecium tetraurelia
Silencing-associated and meiosis-specific small RNA pathways in Paramecium tetraurelia
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DOI：
10.1093/nar/gkn1018
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发表时间：
2009-02-01
影响因子：
14.9
通讯作者：
Meyer, Eric
中科院分区：
文献类型：
--
作者：
Lepere, Gersende;Nowacki, Mariusz;Meyer, Eric
Dicer 和 Dicer 样基因的功能分析以及小 RNA 测序表明，草履虫中描述的两种同源依赖性效应涉及不同的小 RNA 途径。当细胞被喂食双链 RNA (dsRNA) 时，介导转录后基因沉默的 siRNA 被发现包含两个亚类。诱导 dsRNA 的 DCR1 依赖性切割从两条链中产生类似于 23-nt 初级 siRNA，而类似于 24-nt RNA 的不同亚类（其特征是短的非模板聚 A 尾巴）与目标 mRNA 严格反义，表明依赖于 RNA 依赖性 RNA 聚合酶的次级 siRNA。一条完全不同的途径负责有性生殖后发育基因组重排的同源依赖性调节。在减数分裂早期，DCL2 和 DCL3 基因是从所有类型的种系序列（包括外显子、内含子、基因间区域、转座子和内部消除序列）产生类似于 25-nt scnRNA 的高度复杂群体所必需的。显着的 5'-UNG 签名和在位置 21-23 处显示互补签名的小部分表明，scnRNA 作为两端具有 2-nt 3' 突出端的双链体从 dsRNA 前体中裂解，然后优先稳定 5'-UNG 链。
Distinct small RNA pathways are involved in the two types of homology-dependent effects described in Paramecium tetraurelia, as shown by a functional analysis of Dicer and Dicer-like genes and by the sequencing of small RNAs. The siRNAs that mediate post-transcriptional gene silencing when cells are fed with double-stranded RNA (dsRNA) were found to comprise two subclasses. DCR1-dependent cleavage of the inducing dsRNA generates similar to 23-nt primary siRNAs from both strands, while a different subclass of similar to 24-nt RNAs, characterized by a short untemplated poly-A tail, is strictly antisense to the targeted mRNA, suggestive of secondary siRNAs that depend on an RNA-dependent RNA polymerase. An entirely distinct pathway is responsible for homology-dependent regulation of developmental genome rearrangements after sexual reproduction. During early meiosis, the DCL2 and DCL3 genes are required for the production of a highly complex population of similar to 25-nt scnRNAs from all types of germline sequences, including both strands of exons, introns, intergenic regions, transposons and Internal Eliminated Sequences. A prominent 5'-UNG signature, and a minor fraction showing the complementary signature at positions 21-23, indicate that scnRNAs are cleaved from dsRNA precursors as duplexes with 2-nt 3' overhangs at both ends, followed by preferential stabilization of the 5'-UNG strand.