Unlocking fundamental principles of chromatin signalling

真核生物的基因组被组蛋白蛋白覆盖，组蛋白蛋白作为一个信号平台，形成了基因组调控和保护的组成部分。这些信号由组蛋白的翻译后修饰组成，组蛋白有“编写器”和“擦除器”酶，以及专门结合标记的阅读器蛋白。这个项目的重点是一种名为CLR4的酶，它是分裂酵母异染色质系统的核心，这是一个非常有用的模型系统，用于了解染色质信号的基本机制。CLR4沉积组蛋白H3赖氨酸9甲基标记(H3K9me)，这是建立沉默的表观遗传状态所必需的，这种状态可以在不改变潜在DNA序列的情况下从一代传播到下一代。CLR4是在植物和动物中也发现的一个大型蛋白质家族的一部分，SUV39酶在许多不同的生物体中沉积H3K9me标记。在哺乳动物中，这些酶被证明是健康发育所必需的，它们的放松调控与各种癌症有关。我们实验室最近的工作表明，在H3K9附近的残基上泛素化赖氨酸14，可以刺激H3K9上CLR4的活性250倍以上(Stirpe等人)。我们还有证据表明，CLR4上的磷酸化本身可以调节H3K9甲基转移酶的活性。这个项目是一个国际合作努力的一部分，该项目利用我们在高分辨率结构方法方面的专业知识，包括X射线结晶学、核磁共振和冷冻-EM，以可视化和了解这些翻译后修饰如何控制CLR4。我们将通过多核核磁共振和单分子实验来研究该体系的分子动力学。对ClR4 S调控的这种丰富的理解将揭示支配哺乳动物同系物的原则，因此将是推动开发治疗方法的关键。

The genomes of eukaryotic organisms are covered by histone proteins, which act as a signalling platform that forms an integral part of the regulation and protection of the genome. The signals consist of post-translational modifications on histones for which there are "writer" and "eraser" enzymes as well as reader proteins that specifically bind the marks. This project focuses on an enzyme called Clr4 that is at the heart the fission yeast heterochromatin system, a very informative model system for understanding the fundamental mechanisms of signalling on chromatin. Clr4 deposits the histone H3 lysine 9 methyl marks (H3K9me), which are required to establish silent epigenetic states that can be propagated from one generation to the next without changes in the underlying DNA sequence. Clr4 is part of a large protein family also found in plants and animals, the SUV39 enzymes, which deposit H3K9me marks in many different organisms. In mammals, these enzymes have been shown to be required for healthy development and their deregulation is associated with various cancers.Recent work in our laboratory has revealed that ubiquitination on a residue close to H3K9, lysine 14, can stimulate the activity of Clr4 on H3K9 by more than 250-fold (Stirpe et al.). We have furthermore evidence that phosphorylation on Clr4 itself regulates the H3K9 methyltransferase activity.This project is part of an international collaborative effort that leverages our expertise in high-resolution structural approaches including X-ray crystallography, NMR and cryo-EM to visualize and understand how these post-translational modifications control Clr4. We will investigate the molecular dynamics of the system by multinuclear NMR and single-molecule experiments. This rich understanding of Clr4's regulation will inform the principles that govern mammalian homologs and will thereby be key to driving efforts to develop therapeutic approaches.