Institut de biologie de l'École normale supérieure (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France; Université Paris-Saclay, 91190 Orsay, France.
Institut de biologie de l'École normale supérieure (IBENS), École normale supérieure, CNRS, INSERM, Université PSL, Paris, France.
Cell Rep. 2023 Aug 29;42(8):112894. doi: 10.1016/j.celrep.2023.112894. Epub 2023 Jul 28.
While the pivotal role of linker histone H1 in shaping nucleosome organization is well established, its functional interplays with chromatin factors along the epigenome are just starting to emerge. Here we show that, in Arabidopsis, as in mammals, H1 occupies Polycomb Repressive Complex 2 (PRC2) target genes where it favors chromatin condensation and H3K27me3 deposition. We further show that, contrasting with its conserved function in PRC2 activation at genes, H1 selectively prevents H3K27me3 accumulation at telomeres and large pericentromeric interstitial telomeric repeat (ITR) domains by restricting DNA accessibility to Telomere Repeat Binding (TRB) proteins, a group of H1-related Myb factors mediating PRC2 cis recruitment. This study provides a mechanistic framework by which H1 avoids the formation of gigantic H3K27me3-rich domains at telomeric sequences and contributes to safeguard nucleus architecture.
尽管连接组蛋白 H1 在形成核小体组织中的关键作用已得到充分证实，但它与表观基因组中染色质因子的功能相互作用才刚刚开始显现。在这里，我们表明，与哺乳动物一样，在拟南芥中，H1 占据多梳抑制复合物 2（PRC2）靶基因，在这些基因中，它有利于染色质凝聚和 H3K27me3 的沉积。我们进一步表明，与它在 PRC2 激活基因中的保守功能相反，H1 通过限制端粒重复结合（TRB）蛋白对 DNA 的可及性，选择性地防止 H3K27me3 在端粒和大着丝粒间区（ITR）域的积累，TRB 蛋白是一组介导 PRC2 顺式招募的 H1 相关 Myb 因子。这项研究提供了一个机制框架，通过该框架，H1 避免了在端粒序列中形成巨大的富含 H3K27me3 的域，并有助于保护核结构。
