RNA介導(dǎo)DNA甲基化（RdDM）是植物中建立DNA甲基化和引起轉(zhuǎn)基因沉默的重要途徑，它還能夠抑制基因組中可轉(zhuǎn)座元件的移動(dòng),，維持基因組的穩(wěn)定,。
2011年11月8日,，北京生命科學(xué)研究所何新建實(shí)驗(yàn)室在《Cell Research》雜志發(fā)表了題為“An atypical component of RNA-directed DNA methylation machinery has both DNA methylation-dependent and -independent roles in locus-specific transcriptional gene silencing”的研究論文。
此研究通過(guò)遺傳篩選鑒定了一個(gè)編碼RdDM途徑新組分的基因DTF1,。這個(gè)基因的功能缺失突變能夠抑制轉(zhuǎn)錄水平的基因沉默,，減少異染色質(zhì)相關(guān)的24-nt siRNA的積累，改變DNA的甲基化水平,。但是,，有趣的是，在部分RdDM的目標(biāo)序列,，雖然DTF1的突變能夠引起siRNA水平的降低,，并抑制基因沉默，但是它卻并不改變DNA甲基化水平,。DTF1可能代表一類非典型的RdDM組分,，它能通過(guò)依賴DNA甲基化和不依賴DNA甲基化兩種途徑引起轉(zhuǎn)錄水平的基因沉默。除了DNA甲基化修飾之外,，siRNA也可能通過(guò)其它染色質(zhì)修飾方式引起轉(zhuǎn)錄水平的基因沉默,。
該所的劉軍博士、張翠軍博士和美國(guó)普渡大學(xué)朱健康實(shí)驗(yàn)室的研究生白戈是本文的共同第一作者,。論文的其他作者還包括我所的技術(shù)員周進(jìn)興,、張素維、陳慶和普渡大學(xué)的陳偉,、鄧馨（現(xiàn)在中科院植物所工作）和朱健康博士,。何新建博士是本文的通訊作者。該研究由科技部和北京市政府資助,。(生物谷 Bioon.com)
doi:10.1038/cr.2011.173
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An atypical component of RNA-directed DNA methylation machinery has both DNA methylation-dependent and -independent roles in locus-specific transcriptional gene silencing.
Liu J, Bai G, Zhang C, Chen W, Zhou J, Zhang S, Chen Q, Deng X, He XJ, Zhu JK.
RNA-directed DNA methylation (RdDM) is an important de novo DNA methylation pathway in plants. RdDM mediates the transcriptional silencing of many endogenous genomic loci, most of which are transposon related. A forward genetics screen identified DTF1 (DNA-binding transcription factor 1) as a new component for RdDM in Arabidopsis. Loss-of-function mutations in DTF1 release the transcriptional silencing of RdDM target loci and reduce the accumulation of 24-nt small interfering RNAs (siRNAs) from some of the targets. Interestingly, in the dtf1 mutant plants, the release of transcriptional gene silencing at solo-LTR is accompanied by decreased siRNA accumulation but not by reduced DNA methylation. These results suggest that DTF1 is an atypical component of RdDM and has both DNA methylation-dependent and -independent roles in transcriptional gene silencing. We suggest that besides DNA methylation, siRNAs may cause some other uncharacterized epigenetic modifications that lead to transcriptional gene silencing.Cell Research advance online publication 8 November 2011; doi:10.1038/cr.2011.173.
