SESAME-catalyzed H3T11 phosphorylation inhibits Dot1-catalyzed H3K79me3 to regulate autophagy and telomere silencing

The glycolytic enzyme, pyruvate kinase Pyk1 maintains telomere heterochromatin by phosphorylating histone H3T11 (H3pT11), which promotes SIR (silent information regulator) complex binding at telomeres and prevents autophagy-mediated Sir2 degradation. However, the exact action mechanism of H3pT11 is poorly understood. Here, we identify Dot1-catalyzed H3K79 tri-methylation (H3K79me3) as the downstream effector of H3pT11 and uncover how this histone crosstalk regulates autophagy and telomere silencing. Mechanistically, Pyk1-catalyzed H3pT11 directly reduces the binding of Dot1 to chromatin and inhibits Dot1-catalyzed H3K79me3, which leads to transcriptional repression of autophagy genes and reduced autophagy. Despite the antagonism between H3pT11 and H3K79me3, they synergically promote the binding of SIR complex at telomeres to maintain telomere silencing. Furthermore, we identify Reb1 as a telomere-associated factor that recruits Pyk1-containing SESAME (Serine-responsive SAM-containing Metabolic Enzyme) complex to telomere regions to phosphorylate H3T11 and prevent the invasion of H3K79me3 from euchromatin into heterochromatin to maintain telomere silencing. Together, these results uncover a novel histone crosstalk and provide insights into dynamic regulation of silent heterochromatin and autophagy in response to cell metabolism. Overall design: ChIP-Seq examination

糖酵解酶丙酮酸激酶Pyk1通过磷酸化组蛋白H3T11（H3pT11）维持端粒异染色质，该修饰可促进沉默信息调节因子（SIR，silent information regulator）复合物在端粒区域的结合，并阻止自噬介导的Sir2降解。然而，H3pT11的确切作用机制仍有待阐明。本研究鉴定出Dot1催化的H3K79三甲基化（H3K79me3）为H3pT11的下游效应分子，并揭示了该组蛋白串扰如何调控自噬与端粒沉默。从机制层面而言，Pyk1催化的H3pT11可直接降低Dot1与染色质的结合能力，抑制Dot1介导的H3K79me3，进而导致自噬相关基因的转录抑制以及自噬水平降低。尽管H3pT11与H3K79me3之间存在拮抗关系，但二者可协同促进SIR复合物在端粒区域的结合，以维持端粒沉默。此外，本研究鉴定出Reb1作为一种端粒相关因子，可招募携带丝氨酸响应型含SAM代谢酶（SESAME，Serine-responsive SAM-containing Metabolic Enzyme）复合物的Pyk1至端粒区域，通过磷酸化H3T11并阻止H3K79me3从常染色质入侵异染色质，从而维持端粒沉默。综上，本研究揭示了一种新型的组蛋白串扰机制，为响应细胞代谢的沉默异染色质与自噬的动态调控提供了新的研究视角。实验整体设计：染色质免疫共沉淀测序（ChIP-Seq）检测。