Arginine methylation and the cell cycle

在细胞生物学中，需要理解的最重要的概念之一是条件特异性基因转录：细胞根据自己的身份或需要调整它们表达的基因的补体。遗传信息被包装成染色质的方式对真核生物的基因表达有着巨大的影响。因此，转录因子和协同调节因子在一定程度上通过精确调节染色质的结构起作用就不足为奇了。组蛋白的共价修饰，如乙酰化或甲基化，是染色质结构改变的一个主要例子。这种组蛋白翻译后修饰就像“标记”一样，可以改变染色质纤维的生物物理特性，或者作为转录机制的识别平台。我的研究团队致力于揭示监督最基本的细胞生物学过程之一——细胞分裂周期的分子机制。为了更好地理解染色质结构变化与细胞分裂基因转录之间的相互作用，我们最近关注了一个相对未被充分研究的染色质修饰：精氨酸侧链上组蛋白的甲基化。特别是，我们结合了功能基因组学和生化方法来表征Prmt5（蛋白精氨酸甲基转移酶5）所起的作用。这种酶参与组蛋白H3、H4和H2a上特定精氨酸侧链的对称二甲基化，但它也可以使非组蛋白甲基化。此外，我们的新实验结果显示，Prmt5被招募到数百个参与控制细胞增殖的基因的启动子。在这些初步发现的基础上，我们希望启动一个新的nserc资助的研究项目，旨在了解Prmt5和精氨酸二甲基化如何控制细胞行为，特别是它们如何影响细胞分裂周期。我们的项目围绕三大目标展开：***1-研究Prmt5在控制靶基因表达中的作用。Prmt5的作用是诱导还是抑制靶基因？哪些组蛋白精氨酸甲基化标记依赖于靶基因上的Prmt5，基因活性与Prmt5“书写”的各种二甲基精氨酸标记之间是否存在关系？***2-研究Prmt5向其靶基因募集的模式。既然Prmt5不直接与DNA结合，那么它是如何被招募到靶基因上的呢？哪些转录因子或染色质蛋白参与其中？生物信息学和蛋白质组学方法将用于确定候选药物。***3-研究Prmt5非组蛋白靶点在调控靶基因表达中的作用。Prmt5可以甲基化许多非组蛋白。我们将探讨细胞周期调节转录因子的活性是由精氨酸甲基化调节的想法。* * * * * * * *

In cell biology, one of the most important notions to understand is condition-specific gene transcription: the idea that cells adjust the complement of genes they express based on their identity or on their needs. The way genetic information is packaged into chromatin has an immense influence on eukaryotic gene expression. It is not surprising then, that transcription factors and co-regulators work in part by precisely modulating the structure of chromatin. The covalent modification of histones, e.g. by acetylation or methylation, is a prime example of chromatin structural changes. Such histone post-translational modifications work like “marks” that can change the biophysical properties of the chromatin fiber, or serve as recognition platforms for the transcriptional machinery.***My research team works to reveal the molecular mechanisms that oversee one of the most fundamental cell biology processes, the cell division cycle. In an effort to better understand the interplay between chromatin structural changes and the transcription of genes that enable cell division, we have recently focused on a relatively understudied chromatin modification: the methylation of histones on arginine side chains. In particular, we have a combination of functional genomics and biochemical approaches to characterize the role played by the enzyme Prmt5 (Protein arginine methyl-transferase 5). This enzyme is involved in symmetrically di-methylating specific arginine side chains on histones H3, H4 and H2a, but it can also methylate non-histone proteins. Among others, the results of our new experiments have revealed that Prmt5 is recruited to the promoter of hundreds of genes involved in controlling cell proliferation.***Building on these preliminary findings, we want to initiate a new NSERC-funded research program that will be oriented towards understanding how Prmt5 and arginine di-methylation control cell behavior, in particular how they affect the cell division cycle. Our program revolves around three broad goals:***1-Studying the role of Prmt5 in controlling target gene expression. Are target genes induced or repressed by the action of Prmt5? Which histone arginine methylation marks depend on Prmt5 at target genes, and do relationships exist between gene activity and the various di-methyl arginine marks “written” by Prmt5?***2-Studying the mode of recruitment of Prmt5 to its target genes. Since Prmt5 does not bind to DNA directly, how is it recruited to target genes? Which transcription factors or chromatin proteins are involved? Bioinformatics and proteomics approaches will be used to identify candidates.***3-Studying non-histone targets of Prmt5 in the regulation of target gene expression. Prmt5 can methylate a number of non-histone proteins. We will explore the idea that the activity of cell cycle regulatory transcription factors is modulated by arginine methylation. ********