State Key Laboratory of Protein and Plant Gene Research, School of Advanced Agricultural Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China.
Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC), Avenida Américo Vespucio 49, 41092, Seville, Spain.
Nat Commun. 2021 Jan 12;12(1):315. doi: 10.1038/s41467-020-20614-1.
Although it is well established that the Polycomb Group (PcG) complexes maintain gene repression through the incorporation of H2AK121ub and H3K27me3, little is known about the effect of these modifications on chromatin accessibility, which is fundamental to understand PcG function. Here, by integrating chromatin accessibility, histone marks and expression analyses in different Arabidopsis PcG mutants, we show that PcG function regulates chromatin accessibility. We find that H2AK121ub is associated with a less accessible but still permissive chromatin at transcriptional regulation hotspots. Accessibility is further reduced by EMF1 acting in collaboration with PRC2 activity. Consequently, H2AK121ub/H3K27me3 marks are linked to inaccessible although responsive chromatin. In contrast, only-H3K27me3-marked chromatin is less responsive, indicating that H2AK121ub-marked hotspots are required for transcriptional responses. Nevertheless, despite the loss of PcG activities leads to increased chromatin accessibility, this is not necessarily accompanied by transcriptional activation, indicating that accessible chromatin is not always predictive of gene expression.
尽管 Polycomb 组（PcG）复合物通过 H2AK121ub 和 H3K27me3 的掺入来维持基因抑制已得到充分证实，但对于这些修饰对染色质可及性的影响知之甚少，而染色质可及性是理解 PcG 功能的基础。在这里，我们通过整合不同拟南芥 PcG 突变体中的染色质可及性、组蛋白标记和表达分析，表明 PcG 功能调节染色质可及性。我们发现 H2AK121ub 与转录调控热点处的一种较少可及但仍具有许可性的染色质相关。EMF1 与 PRC2 活性协同作用进一步降低了可及性。因此，H2AK121ub/H3K27me3 标记与不可访问但有反应性的染色质相关。相比之下，仅具有 H3K27me3 标记的染色质反应性较低，表明 H2AK121ub 标记的热点对于转录反应是必需的。然而，尽管 PcG 活性的丧失导致染色质可及性增加，但这并不一定伴随着转录激活，表明可及性染色质并不总是基因表达的预测因子。
