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：即细胞根据自己的身份或需求调整其表达的基因的补体。遗传信息被包装到染色质中的方式对真核基因的表达有巨大的影响。因此，转录因子和辅助调节因子在一定程度上通过精确调节染色质的结构发挥作用也就不足为奇了。组蛋白的共价修饰，例如通过乙酰化或甲基化，是染色质结构变化的主要例子。这种组蛋白翻译后修饰的工作原理就像是可以改变染色质纤维生物物理性质的“标记”，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。为了更好地了解染色质结构变化和使细胞分裂的基因转录之间的相互作用，我们最近专注于一种相对研究较少的染色质修饰：精氨酸侧链上的组蛋白甲基化。特别是，我们结合了功能基因组学和生化方法来表征酶PRMT5(蛋白质精氨酸甲基转移酶5)所起的作用。这种酶参与了组蛋白H3、H4和H2A上特定精氨酸侧链的对称甲基化，但它也可以甲基化非组蛋白。其中，我们的新实验结果显示，PRMT5被招募到参与控制细胞增殖的数百个基因的启动子中。*在这些初步发现的基础上，我们希望启动一个由NSERC资助的新研究计划，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。我们的计划围绕着三个广泛的目标：*1-研究PRMT5在控制靶基因表达中的作用。靶基因是被PRMT5诱导还是被抑制？哪些组蛋白精氨酸甲基化标记依赖于PRMT5的靶基因，以及基因活性与PRMT5所写的各种二甲基精氨酸标记之间是否存在关系？*2-研究PRMT5对其靶基因的募集方式。既然PRMT5不直接与DNA结合，它是如何被招募到靶向基因的？哪些转录因子或染色质蛋白参与其中？将使用生物信息学和蛋白质组学方法来确定候选基因。*3-研究PRMT5在靶基因表达调控中的非组蛋白靶标。PRMT5可以甲基化一些非组蛋白蛋白。我们将探讨细胞周期调节转录因子的活性受精氨酸甲基化调节的观点。********

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. ********