Unlocking fundamental principles of chromatin signalling

真核生物的基因组被组蛋白覆盖，组蛋白作为信号平台，构成了基因组调节和保护的组成部分。这些信号由组蛋白上的翻译后修饰组成，组蛋白上有“书写”酶和“擦除”酶，以及特异性结合标记的解读蛋白。这个项目的重点是一种叫做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，用于理解染色质信号传导的基本机制。Clr4沉积了组蛋白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基础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蛋白质家族的一部分，SUV39酶，它在许多不同的生物体中沉积H3K9me标记。在哺乳动物中，这些酶已被证明是健康发育所必需的，而它们的失调与各种癌症有关。我们实验室最近的工作表明，靠近H3K9的残基赖氨酸14的泛素化可以刺激H3K9上Clr4的活性超过250倍（Stirpe等人）。我们有进一步的证据表明，Clr4磷酸化本身调节H3K9甲基转移酶的活性。该项目是一个国际合作项目的一部分，利用我们在高分辨率结构方法方面的专业知识，包括x射线晶体学，核磁共振和冷冻电镜，以可视化和理解这些翻译后修饰如何控制Clr4。我们将通过多核磁共振和单分子实验来研究该体系的分子动力学。对Clr4调控的丰富理解将为管理哺乳动物同源物的原则提供信息，从而将成为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.