Pintacuda Greta, Wei Guifeng, Roustan Chloë, Kirmizitas Burcu Anil, Solcan Nicolae, Cerase Andrea, Castello Alfredo, Mohammed Shabaz, Moindrot Benoît, Nesterova Tatyana B, Brockdorff Neil
Developmental Epigenetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Posttranscriptional Networks in Infection and Cell Cycle Progression, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Mol Cell. 2017 Dec 7;68(5):955-969.e10. doi: 10.1016/j.molcel.2017.11.013.
The Polycomb-repressive complexes PRC1 and PRC2 play a key role in chromosome silencing induced by the non-coding RNA Xist. Polycomb recruitment is initiated by the PCGF3/5-PRC1 complex, which catalyzes chromosome-wide H2A lysine 119 ubiquitylation, signaling recruitment of other PRC1 complexes, and PRC2. However, the molecular mechanism for PCGF3/5-PRC1 recruitment by Xist RNA is not understood. Here we define the Xist RNA Polycomb Interaction Domain (XR-PID), a 600 nt sequence encompassing the Xist B-repeat element. Deletion of XR-PID abolishes Xist-dependent Polycomb recruitment, in turn abrogating Xist-mediated gene silencing and reversing Xist-induced chromatin inaccessibility. We identify the RNA-binding protein hnRNPK as the principal XR-PID binding factor required to recruit PCGF3/5-PRC1. Accordingly, synthetically tethering hnRNPK to Xist RNA lacking XR-PID is sufficient for Xist-dependent Polycomb recruitment. Our findings define a key pathway for Polycomb recruitment by Xist RNA, providing important insights into mechanisms of chromatin modification by non-coding RNA.
多梳抑制复合物PRC1和PRC2在由非编码RNA Xist诱导的染色体沉默中起关键作用。多梳蛋白的招募由PCGF3/5-PRC1复合物启动，该复合物催化全染色体范围的H2A赖氨酸119泛素化，标志着其他PRC1复合物和PRC2的招募。然而，Xist RNA招募PCGF3/5-PRC1的分子机制尚不清楚。在这里，我们定义了Xist RNA多梳相互作用结构域（XR-PID），这是一个包含Xist B重复元件的600 nt序列。删除XR-PID会消除Xist依赖的多梳蛋白招募，进而废除Xist介导的基因沉默并逆转Xist诱导的染色质不可及性。我们确定RNA结合蛋白hnRNPK是招募PCGF3/5-PRC1所需的主要XR-PID结合因子。因此，将hnRNPK合成拴系到缺乏XR-PID的Xist RNA上足以实现Xist依赖的多梳蛋白招募。我们的研究结果定义了Xist RNA招募多梳蛋白的关键途径，为非编码RNA介导的染色质修饰机制提供了重要见解。
