Chromatin Modification by Histone Ubiquitination and Methylations

描述（由申请人提供）：我们的长期目标是了解基因表达的失调如何导致肿瘤发生，并了解如何修复转录缺陷。我们一直在研究酵母S.啤酒。组蛋白的无数修饰对于基因表达的适当调节是重要的。在这些组蛋白修饰中重要的是H3在其第4和第79个赖氨酸（H3 K4和H3 K79）上的甲基化，其与转录活性基因相关。这些残基的甲基化需要组蛋白H2 B被Rad 6/Bre 1蛋白复合物单泛素化，这是一种从酵母到人类都保守的组蛋白串扰途径。我们确定了与Set 1（COMPASS）作为酵母H3 K4甲基转移酶相关的蛋白质复合物。Set 1是人类混合谱系白血病蛋白的同源物，由在多种侵袭性急性白血病中重排的MLL基因编码。我们现在知道，人类MLL蛋白也存在于能够催化H3 K4甲基化的COMPASS样复合物中。我们已经开发了一个强大的筛选酵母蛋白质组，以确定适当的H3 K4甲基化所需的机器。我们建议建立在这个基础上，进一步定义的分子机制参与安装和删除组蛋白H3 K4和K79甲基化，催化COMPASS和Dot 1，分别。我们还建议利用我们的生物化学，酶学和遗传学专业知识来开发H3 K4和K79甲基化酶和脱甲基酶的抑制剂。此类抑制剂可用作先导化合物，用于开发治疗白血病的靶向治疗剂。 我们的具体目标是： 目的1：通过COMPASS和Dot 1研究组蛋白H2 B单泛素化对组蛋白甲基化的调控作用。 目的2：定义参与H3 K4和K79去甲基化的机制。 目的3：鉴定H3 K4甲基化和去甲基化酶的小分子抑制剂。 我们的酵母研究的继续不仅有望导致更好地理解H3 K4和K79甲基化的不同功能和生理意义，而且还建立了组蛋白甲基化的基础生物学和涉及MLL基因的染色体易位引起的白血病的治疗之间的联系。

DESCRIPTION (provided by applicant): Our long-term goal is to understand how misregulation of gene expression leads to oncogenesis, and to learn how to repair transcriptional defects. We have been studying the mechanisms of chromatin modifications and control of transcriptional elongation in the yeast S. cerevisiae. Myriad modifications of histones are important for proper regulation of gene expression. Important among these histone modifications are methylation of H3 on its 4th and 79th lysines (H3K4 and H3K79), which are associated with transcriptionally active genes. Methylation of these residues requires histone H2B to be monoubiquitinated by the Rad6/Bre1 protein complex, a histone cross-talk pathway that is conserved from yeasts to humans. We identified a complex of proteins associated with Set1 (COMPASS) as the yeast H3K4 methyltransferase. Set1 is the homologue of the human mixed lineage leukemia protein, encoded by the MLL gene that is rearranged in a variety of aggressive acute leukemias. We now know that human MLL protein is also found in a COMPASS-like complex capable of catalyzing the methylation of H3K4. We have developed a robust screen of the yeast proteome to identify the machinery required for proper H3K4 methylation. We propose to build on this foundation to define further the molecular machinery involved in the installation and removal of histone H3K4 and K79 methylations, catalyzed by COMPASS and Dot1, respectively. We also propose to leverage our biochemical, enzymological, and genetical expertise to develop inhibitors of H3K4 and K79 methylases and demethylases. Such inhibitors may be useful as lead compounds for the development of targeted therapeutic agents for the treatment of leukemia. Our specific aims are: Aim 1: Define how monoubiquitination of histone H2B regulates histone methylation by COMPASS and Dot1. Aim 2: Define the machinery involved in H3K4 and K79 demethylation. Aim 3: Identify small molecule inhibitors of H3K4 methylating and demethylating enzymes. Continuation of our yeast studies promises not only to lead to a better understanding of the diverse functional and physiological significance of H3K4 and K79 methylations, but also to forge a link between the basic biology of histone methylation and the treatment of leukemia caused by chromosomal translocations involving the MLL gene.