Laboratoire Génome et Développement des Plantes, Centre National de la Recherche Scientifique/Université de Perpignan via Domitia, UMR5096, Perpignan, France.
Mol Cell. 2012 Oct 12;48(1):121-32. doi: 10.1016/j.molcel.2012.07.027. Epub 2012 Aug 30.
In Arabidopsis, transcriptional gene silencing (TGS) can be triggered by 24 nt small-interfering RNAs (siRNAs) through the RNA-directed DNA methylation (RdDM) pathway. By functional analysis of NERD, a GW repeat- and PHD finger-containing protein, we demonstrate that Arabidopsis harbors a second siRNA-dependent DNA methylation pathway targeting a subset of nonconserved genomic loci. The activity of the NERD-dependent pathway differs from RdDM by the fact that it relies both on silencing-related factors previously implicated only in posttranscriptional gene silencing (PTGS), including RNA-DEPENDENT RNA POLYMERASE1/6 and ARGONAUTE2, and most likely on 21 nt siRNAs. A central role for NERD in integrating RNA silencing and chromatin signals in transcriptional silencing is supported by data showing that it binds both to histone H3 and AGO2 proteins and contributes to siRNA accumulation at a NERD-targeted locus. Our results unravel the existence of a conserved chromatin-based RNA silencing pathway encompassing both PTGS and TGS components in plants.
在拟南芥中，转录基因沉默（TGS）可以通过 RNA 指导的 DNA 甲基化（RdDM）途径被 24 个核苷酸的小干扰 RNA（siRNA）触发。通过对含有 GW 重复和 PHD 指结构域的蛋白 NERD 的功能分析，我们证明拟南芥还存在另一种依赖 siRNA 的 DNA 甲基化途径，该途径靶向一组非保守的基因组位点。NERD 依赖的途径与 RdDM 的活性不同，它既依赖于以前只在转录后基因沉默（PTGS）中涉及的沉默相关因子，包括 RNA 依赖性 RNA 聚合酶 1/6 和 ARGONAUTE2，也可能依赖于 21 个核苷酸的 siRNA。NERD 在整合 RNA 沉默和染色质信号以实现转录沉默中的核心作用得到了以下数据的支持：它既与组蛋白 H3 和 AGO2 蛋白结合，又有助于在 NERD 靶向的基因座积累 siRNA。我们的结果揭示了在植物中存在一种保守的基于染色质的 RNA 沉默途径，它包含了 PTGS 和 TGS 的成分。
