The Histone H3 Lysine 9 Methyltransferases G9a and GLP Regulate Polycomb Repressive Complex 2-Mediated Gene Silencing [RNA-Seq]

G9a/GLP and Polycomb Repressive Complex 2 (PRC2) are two major epigenetic silencing machineries, which in particular methylate histone H3 on lysines 9 and 27 (H3K9 and H3K27), respectively. Although evidence of a crosstalk between H3K9 and H3K27 methylations has started to emerge, their actual interplay remains elusive. Here, we show that PRC2 and G9a/GLP interact physically and functionally. Moreover, combining different genome-wide approaches, we demonstrate that Ezh2 and G9a/GLP share an important number of common genomic targets, encoding developmental and neuronal regulators. Furthermore, we show that G9a enzymatic activity modulates PRC2 genomic recruitment to a subset of its target genes. Taken together, our findings demonstrate an unanticipated interplay between two main histone lysine methylation mechanisms, which cooperate to maintain silencing of a subset of developmental genes. Overall design: RNA-seq has been perform in triplicate on mES cell (TT2 : Wildtype, and KO G9a-/-)

G9a/GLP与多梳抑制复合体2（Polycomb Repressive Complex 2，PRC2）是两类核心表观遗传沉默系统，二者分别可对组蛋白H3的赖氨酸9位（H3K9）与赖氨酸27位（H3K27）进行甲基化修饰。尽管H3K9与H3K27甲基化之间存在交叉对话的证据已逐渐显现，但二者实际的相互调控机制仍不明确。本研究证实，PRC2与G9a/GLP在物理互作与功能层面均存在关联。此外，通过整合多种全基因组学研究手段，我们证明Ezh2与G9a/GLP共享大量共同的基因组靶标，这些靶标编码发育调控因子与神经元调控因子。进一步实验表明，G9a的酶催化活性可调控PRC2对部分靶基因的基因组招募。综上，本研究揭示了两种主要组蛋白赖氨酸甲基化机制之间此前未被发现的相互作用，二者协同维持了部分发育基因的沉默状态。整体实验设计：以小鼠胚胎干细胞（mouse embryonic stem cell，mES cell）TT2野生型与G9a敲除型（G9a-/-）为材料，完成三组生物学重复的RNA测序（RNA-seq）。