Pradhan Sunil Kumar, Zhang Hui, Kolobynina Ksenia G, Rapp Alexander, Arroyo Maria, Cardoso M Cristina
Cell Biology and Epigenetics, Department of Biology, Technical University of Darmstadt, 64287, Darmstadt, Germany.
EMBO Rep. 2025 Sep 8. doi: 10.1038/s44319-025-00575-6.
The flexibility of the spatio-temporal genome replication program during development and disease highlights the regulatory role of plastic epigenetic mechanisms over genetic determinants. Histone post-translational modifications are broadly implicated in replication timing control, yet the specific mechanisms through which individual histone marks influence replication dynamics, particularly in heterochromatin, remain unclear. Here, we demonstrate that H3K36me3 dynamically enriches at pericentromeric heterochromatin, composed of major satellite DNA repeats, prior to replication during mid S phase in mouse embryonic stem cells. By knocking down lysine 36-specific methyltransferases or by targeting the H3K36M oncohistone to pericentromeric heterochromatin, we reduce global or local H3K36me3 levels, respectively, revealing its essential role in preserving the replication timing of constitutive heterochromatin. Loss of H3K36me3 accompanies increased RNA polymerase II serine-5 phosphorylation and lowered major satellite RNA levels, indicating transcriptional dysregulation. Notably, we identify a strand-specific contribution of major satellite forward transcripts in regulating the replication timing of constitutive heterochromatin and maintaining chromatin stability, highlighting the importance of non-coding RNAs as critical regulators of replication timing.
时空基因组复制程序在发育和疾病过程中的灵活性凸显了可塑性表观遗传机制对遗传决定因素的调控作用。组蛋白翻译后修饰广泛参与复制时间控制，然而，单个组蛋白标记影响复制动态的具体机制，尤其是在异染色质中，仍不清楚。在这里，我们证明在小鼠胚胎干细胞S期中期复制之前，H3K36me3在由主要卫星DNA重复序列组成的着丝粒周围异染色质上动态富集。通过敲低赖氨酸36特异性甲基转移酶或将H3K36M癌组蛋白靶向到着丝粒周围异染色质，我们分别降低了整体或局部H3K36me3水平，揭示了其在维持组成型异染色质复制时间方面的重要作用。H3K36me3的缺失伴随着RNA聚合酶II丝氨酸-5磷酸化的增加和主要卫星RNA水平的降低，表明转录失调。值得注意的是，我们确定了主要卫星正向转录本在调节组成型异染色质复制时间和维持染色质稳定性方面的链特异性贡献，突出了非编码RNA作为复制时间关键调节因子的重要性。
