将 RNA 指导的 DNA 甲基化信号转导为拟南芥中的抑制性组蛋白标记。
Transduction of RNA-directed DNA methylation signals to repressive histone marks in Arabidopsis thaliana.
机构信息
Division of Genome and Biodiversity Research, National Institute of Agrobiological Sciences, Tsukuba, Japan.
出版信息
EMBO J. 2010 Jan 20;29(2):352-62. doi: 10.1038/emboj.2009.374. Epub 2009 Dec 10.
RNA-directed modification of histones is essential for the maintenance of heterochromatin in higher eukaryotes. In plants, cytosine methylation is an additional factor regulating inactive chromatin, but the mechanisms regulating the coexistence of cytosine methylation and repressive histone modification remain obscure. In this study, we analysed the mechanism of gene silencing mediated by MORPHEUS' MOLECULE1 (MOM1) of Arabidopsis thaliana. Transcript profiling revealed that the majority of up-regulated loci in mom1 carry sequences related to transposons and homologous to the 24-nt siRNAs accumulated in wild-type plants that are the hallmarks of RNA-directed DNA methylation (RdDM). Analysis of a single-copy gene, SUPPRESSOR OF drm1 drm2 cmt3 (SDC), revealed that mom1 activates SDC with concomitant reduction of di-methylated histone H3 lysine 9 (H3K9me2) at the tandem repeats in the promoter region without changes in siRNA accumulation and cytosine methylation. The reduction of H3K9me2 is not observed in regions flanking the tandem repeats. The results suggest that MOM1 transduces RdDM signals to repressive histone modification in the core region of RdDM.
RNA 指导的组蛋白修饰对于高等真核生物异染色质的维持是必不可少的。在植物中，胞嘧啶甲基化是调节失活染色质的另一个因素，但调节胞嘧啶甲基化和抑制性组蛋白修饰共存的机制仍不清楚。在这项研究中，我们分析了拟南芥 MORPHEUS' MOLECULE1 (MOM1)介导的基因沉默机制。转录谱分析显示，在 mom1 中上调的大多数基因座携带与转座子相关的序列，与在野生型植物中积累的 24nt siRNAs 同源，这是 RNA 指导的 DNA 甲基化 (RdDM) 的标志。对单个拷贝基因 SUPPRESSOR OF drm1 drm2 cmt3 (SDC) 的分析表明，mom1 激活了 SDC，同时在启动子区域的串联重复序列中降低了二甲基化组蛋白 H3 赖氨酸 9 (H3K9me2)，而 siRNA 积累和胞嘧啶甲基化没有变化。在串联重复序列侧翼的区域中没有观察到 H3K9me2 的减少。结果表明，MOM1 将 RdDM 信号转导到 RdDM 的核心区域的抑制性组蛋白修饰。
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