Structure and Function of SET Domain Methyltransferases

描述（由申请人提供）：组蛋白是染色质中组织和紧密核DNA的主要支架蛋白。这些蛋白质经历了多种类型的化学修饰，这些修饰控制着细胞核中的各种过程。氨基酸赖氨酸的甲基化发生在几种组蛋白中，并与基因表达调控以及DNA修复过程和细胞分裂有关。组蛋白赖氨酸甲基转移酶（HKMTs）是催化组蛋白中特定赖氨酸甲基化的酶。hkmt已被证明是基因表达的正调控因子和负调控因子，这取决于它们在组蛋白中甲基化的特定赖氨酸。最近，一些HKMTs被证明可以甲基化转录因子（激活基因表达的DNA结合蛋白），这表明这些酶在控制转录方面的作用比以前认为的要广泛。这些酶与多种癌症之间的直接关系强调了hkmt在调节基因表达方面的重要性。一些hkmt的缺失、突变或过度表达与恶性肿瘤如白血病、前列腺癌、乳腺癌、肺癌、结肠直肠癌和肝癌有关。为了深入了解HKMTs在转录调控中的功能以及这些酶的破坏如何导致癌症，我们提出了几个实验来表征它们的蛋白质底物特异性，并阐明它们甲基化核蛋白中特定赖氨酸残基的化学机制。为了实现这些目标，我们将结合生物化学和结构生物学来确定这些酶与其蛋白质底物结合的分子结构。综上所述，这项研究不仅将为细胞核中hkmt的功能提供新的见解，而且将为开发针对这些酶的特异性抑制剂以治疗癌症提供途径。目的1：通过对一种被称为Rubisco大亚单位甲基转移酶（LSMT）的植物HKMT同源物的生化和结构研究，确定HKMT赖氨酸甲基化的化学机制。目的2：通过结构和生化技术确定人类组蛋白和转录因子甲基转移酶SET7/9的底物特异性。目的3：确定人类set的结构和底物特异性，这是一种在细胞分裂过程中调节基因沉默和适当染色体分离的关键HKMT。

DESCRIPTION (provided by applicant): Histones are the major scaffolding proteins which organize and compact nuclear DNA in chromatin. These proteins undergo numerous types of chemical modifications that govern a variety of processes in the nucleus. Methylation of the amino acid lysine occurs in several histones and has been linked to the regulation of gene expression as well as in DNA repair processes and cell division. Histone lysine methyltransferases (HKMTs) are enzymes that catalyze the methylation of specific lysines within histones. HKMTs have been shown to function as both positive and negative regulators of gene expression, depending on the specific lysine that they methylate in histones. Recently, some HKMTs have been shown to methylate transcription factors (DNA binding proteins that activate gene expression), suggesting that these enzymes have broader roles in controlling transcription than previously believed. The importance of HKMTs in regulating gene expression is underscored by direct relationships between these enzymes and numerous forms of cancer. Deletions, mutations, or over-expression of several HKMTs have been linked malignancies such as leukemias and prostate, breast, lung, colorectal, and hepatic cancers. In order to gain insight into the functions of HKMTs in transcriptional regulation and how disruption of these enzymes can lead to cancer, we propose several experiments to characterize their protein substrate specificities and elucidate the chemical mechanism through which they methylate specific lysine residues in nuclear proteins. To achieve these goals, we will use a combination of biochemistry and structural biology in which we will determine the molecular structures of these enzymes bound to their protein substrates. Taken together, this research will provide not only novel insights into the functions of HKMTs in the nucleus, but will also provide avenues for the development of specific inhibitors against these enzymes in the treatment of cancer. Aim1: Determine the chemical mechanism of lysine methylation of HKMTs via biochemical and structural studies of a plant HKMT homolog known as Rubisco large subunit methyltransferase (LSMT). Aim2: Determine the substrate specificity of human SET7/9, a histone and transcription factor methyltransferase, through structural and biochemical techniques. Aim3: Determine the structure and substrate specificity of human SETS, an HKMT that is pivotal in regulating gene silencing and proper chromosome separation during cell division.