State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, Tianjin 300350, China.
State Key Laboratory of Medicinal Chemical Biology, College of Life Science, Nankai University, Tianjin, Tianjin 300071, China.
Nucleic Acids Res. 2023 Sep 22;51(17):8970-8986. doi: 10.1093/nar/gkad640.
Dot1l is a histone methyltransferase without a SET domain and is responsible for H3K79 methylation, which marks active transcription. In contradiction, Dot1l also participates in silencing gene expression. The target regions and mechanism of Dot1l in repressing transcription remain enigmatic. Here, we show that Dot1l represses endogenous retroviruses in embryonic stem cells (ESCs). Specifically, the absence of Dot1l led to the activation of MERVL, which is a marker of 2-cell-like cells. In addition, Dot1l deletion activated the 2-cell-like state and predisposed ESCs to differentiate into trophectoderm lineage. Transcriptome analysis revealed activation of 2-cell genes and meiotic genes by Dot1l deletion. Mechanistically, Dot1l interacted with and co-localized with Npm1 on MERVL, and depletion of Npm1 similarly augmented MERVL expression. The catalytic activity and AT-hook domain of Dot1l are important to suppress MERVL. Notably, Dot1l-Npm1 restricts MERVL by regulating protein level and deposition of histone H1. Furthermore, Dot1l is critical for Npm1 to efficiently interact with histone H1 and inhibit ubiquitination of H1 whereas Npm1 is essential for Dot1l to interact with MERVL. Altogether, we discover that Dot1l represses MERVL through chaperoning H1 by collaborating with Npm1. Importantly, our findings shed light on the non-canonical transcriptional repressive role of Dot1l in ESCs.
Dot1l 是一种没有 SET 结构域的组蛋白甲基转移酶，负责 H3K79 甲基化，该修饰标志着转录活性。与之矛盾的是，Dot1l 也参与基因表达沉默。Dot1l 抑制转录的靶区和机制仍不清楚。在这里，我们发现 Dot1l 在胚胎干细胞（ESCs）中抑制内源性逆转录病毒。具体来说，Dot1l 的缺失导致 MERVL 的激活，MERVL 是 2 细胞样细胞的标志物。此外，Dot1l 的缺失激活了 2 细胞样状态，并使 ESCs 易于向滋养外胚层谱系分化。转录组分析显示，Dot1l 的缺失激活了 2 细胞基因和减数分裂基因。在机制上，Dot1l 与 Npm1 在 MERVL 上相互作用并共定位，Npm1 的耗竭同样增强了 MERVL 的表达。Dot1l 的催化活性和 AT 钩结构域对于抑制 MERVL 至关重要。值得注意的是，Dot1l-Npm1 通过调节 MERVL 的蛋白水平和组蛋白 H1 的沉积来限制 MERVL。此外，Dot1l 对于 Npm1 与组蛋白 H1 高效相互作用和抑制 H1 的泛素化至关重要，而 Npm1 对于 Dot1l 与 MERVL 的相互作用是必需的。总之，我们发现 Dot1l 通过与 Npm1 合作来通过 chaperoning H1 来抑制 MERVL。重要的是，我们的发现揭示了 Dot1l 在 ESCs 中具有非典型的转录抑制作用。
