RNA-mediated trans-communication can establish paramutation at the b1 locus in maize
RNA-mediated trans-communication can establish paramutation at the b1 locus in maize
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DOI：
10.1073/pnas.1007972107
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发表时间：
2010-07-20
影响因子：
11.1
通讯作者：
Chandler, Vicki L.
中科院分区：
文献类型：
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作者：
Arteaga-Vazquez, Mario;Sidorenko, Lyudmila;Chandler, Vicki L.
副突变是等位基因之间的表观遗传信息转移，导致一个等位基因表达的可遗传变化。在玉米中的b1位点的副突变需要7个非编码串联重复序列（b1 TR）位于类似于100 kb上游的转录起始位点的b1，和副突变所需的几个基因的突变牵连RNA介导的机制。介导副突变基因（mediator of paramutation，mop 1）编码一种与RNA依赖的RNA聚合酶密切相关的蛋白质，是副突变所必需的。在此，我们研究了mop 1和从b1 TR序列产生的siRNA的潜在功能。从b1 TR序列产生siRNA依赖于功能性mop 1基因，但重复序列的转录不依赖于mop 1。进一步的核转录分析表明，b1 TR序列可能主要由RNA聚合酶II转录。为了解决b1 TR-siRNA的产生是否与副突变相关，我们检查了不能发生副突变的等位基因中的siRNA产生。不能参与副突变的等位基因也产生b1 TR-siRNA，这表明b1 TR-siRNA不足以在所分析的组织中进行副突变。然而，当b1 TR-siRNA由表达发夹RNA的转基因产生时，可以重现b1副突变。我们假设b1 TR-siRNA或dsRNA模板介导了等位基因之间的反式通讯，从而建立了副突变。此外，我们发现了mop 1在microRNA（miRNA）的一个子集的生物发生中的作用，并表明它在初级miRNA转录物的产生水平上发挥作用。
Paramutation is the epigenetic transfer of information between alleles that leads to the heritable change of expression of one allele. Paramutation at the b1 locus in maize requires seven noncoding tandem repeat (b1TR) sequences located similar to 100 kb upstream of the transcription start site of b1, and mutations in several genes required for paramutation implicate an RNA-mediated mechanism. The mediator of paramutation (mop1) gene, which encodes a protein closely related to RNA-dependent RNA polymerases, is absolutely required for paramutation. Herein, we investigate the potential function of mop1 and the siRNAs that are produced from the b1TR sequences. Production of siRNAs from the b1TR sequences depends on a functional mop1 gene, but transcription of the repeats is not dependent on mop1. Further nuclear transcription assays suggest that the b1TR sequences are likely transcribed predominantly by RNA polymerase II. To address whether production of b1TR-siRNAs correlated with paramutation, we examined siRNA production in alleles that cannot undergo paramutation. Alleles that cannot participate in paramutation also produce b1TR-siRNAs, suggesting that b1TR-siRNAs are not sufficient for paramutation in the tissues analyzed. However, when b1TR-siRNAs are produced from a transgene expressing a hairpin RNA, b1 paramutation can be recapitulated. We hypothesize that either the b1TR-siRNAs or the dsRNA template mediates the trans-communication between the alleles that establishes paramutation. In addition, we uncovered a role for mop1 in the biogenesis of a subset of microRNAs (miRNAs) and show that it functions at the level of production of the primary miRNA transcripts.