Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-University (LMU) Munich, Großhaderner Straße 9, 82152, Martinsried, Germany.
Protein Analysis Unit, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-University (LMU) Munich, Großhaderner Straße 9, 82152, Martinsried, Germany.
Nat Commun. 2021 Oct 14;12(1):5996. doi: 10.1038/s41467-021-26288-7.
Endogenous retroviruses (ERVs) comprise a significant portion of mammalian genomes. Although specific ERV loci feature regulatory roles for host gene expression, most ERV integrations are transcriptionally repressed by Setdb1-mediated H3K9me3 and DNA methylation. However, the protein network which regulates the deposition of these chromatin modifications is still incompletely understood. Here, we perform a genome-wide single guide RNA (sgRNA) screen for genes involved in ERV silencing and identify the GHKL ATPase protein Morc3 as a top-scoring hit. Morc3 knock-out (ko) cells display de-repression, reduced H3K9me3, and increased chromatin accessibility of distinct ERV families. We find that the Morc3 ATPase cycle and Morc3 SUMOylation are important for ERV chromatin regulation. Proteomic analyses reveal that Morc3 mutant proteins fail to interact with the histone H3.3 chaperone Daxx. This interaction depends on Morc3 SUMOylation and Daxx SUMO binding. Notably, in Morc3 ko cells, we observe strongly reduced histone H3.3 on Morc3 binding sites. Thus, our data demonstrate Morc3 as a critical regulator of Daxx-mediated histone H3.3 incorporation to ERV regions.
内源性逆转录病毒 (ERVs) 构成了哺乳动物基因组的重要组成部分。虽然特定的 ERV 基因座具有调节宿主基因表达的作用，但大多数 ERV 整合被 Setdb1 介导的 H3K9me3 和 DNA 甲基化转录抑制。然而，调节这些染色质修饰沉积的蛋白质网络仍然不完全清楚。在这里，我们进行了全基因组单引导 RNA (sgRNA) 筛选，以鉴定参与 ERV 沉默的基因，并确定 GHKL ATP 酶蛋白 Morc3 为得分最高的命中。Morc3 敲除 (ko) 细胞显示出去抑制、H3K9me3 减少和不同 ERV 家族的染色质可及性增加。我们发现 Morc3 的 ATP 酶循环和 Morc3 的 SUMO 化对于 ERV 染色质调控很重要。蛋白质组学分析表明，Morc3 突变蛋白不能与组蛋白 H3.3 伴侣 Daxx 相互作用。这种相互作用依赖于 Morc3 的 SUMO 化和 Daxx 的 SUMO 结合。值得注意的是，在 Morc3 ko 细胞中，我们观察到 Morc3 结合位点上的组蛋白 H3.3 明显减少。因此，我们的数据表明 Morc3 是 Daxx 介导的组蛋白 H3.3 掺入 ERV 区域的关键调节因子。
