Mutations of Chromatin and its Modifying Machineries in Malignancies

 描述(申请人提供)：我们的研究集中在Set1/MLL蛋白家族的分子功能和生化特性的表征，以及它们的嵌合体和突变与儿童白血病和其他形式的癌症是如何相关的。我们还重点研究了染色质和转录延长机制在发育基因表达调控中的作用，以及它们活动的错误调控如何与恶性肿瘤相关。我们希望我们的分子研究将通过表观遗传调节机制促进我们对基于重排和基于突变的癌症的分子机制的理解。我们的生化和分子研究表明，酵母中的Set1存在于能够甲基化组蛋白H3(H3K4)的赖氨酸4的Set1/Compass复合体中。我们证明了果蝇细胞有三个Set1相关蛋白，哺乳动物细胞有六个Set1相关蛋白，它们都存在于能够甲基化组蛋白H3K4的指南针状成分中。此外，考虑到许多MLL易位配对之间几乎没有序列同源性，多年来，人们一直不清楚为什么MLL易位到如此多无关基因导致白血病的发病。我们对MLL-嵌合体纯化的生化研究表明，许多MLL易位伙伴是同一大分子复合体的一部分，我们称之为超级延长复合体(SEC)。我们证明，在SEC亚基的任何一个亚基内的MLL易位导致SEC错误地招募到MLL靶基因，并扰乱这些基因的转录检查点控制，触发白血病的生长。此外，最近对癌症体细胞突变的编目发现，在血液系统恶性肿瘤和实体瘤中，MLL1-4和Set1A/B复合体的成分都存在大量突变。然而，我们对指南针家族在不同癌症中发生突变的原因知之甚少。鉴于在过去的17年里，我们已经针对这些因子及其相关蛋白质、染色质和其他染色质修饰物在多个模型系统中开发了一套奇妙的试剂和工具；我的实验室处于非常独特的位置，可以定义这些因子参与癌症发病的分子基础，以达到靶向治疗的目的。因此，R35应用的目标是完整的COMPASS家族的分子和生化特征，超级延伸复合体(SEC)内的易位伙伴，染色质本身在基因表达和发育调节中的作用，以及它们的突变如何在人类癌症的发病机制中做出贡献。

 DESCRIPTION (provided by applicant): Our studies have focused on the characterization of the molecular functions and biochemical properties of the Set1/MLL family of proteins and how their chimeras and mutations are associated with childhood leukemia and other forms of cancer. We have also focused on the role of chromatin and transcriptional elongation machinery in the regulation of developmental gene expression and how the misregulation of their activities is associated with malignancies. Our hope is that our molecular studies will advance our understanding of the molecular mechanisms of rearrangement-based and mutation-based cancer through the epigenetic regulators. Our biochemical and molecular studies demonstrated that Set1 in yeast exists in the Set1/COMPASS complex capable of methylating lysine 4 of histone H3 (H3K4). We demonstrated that Drosophila cells possess three Set1-related proteins and mammalian cells have six Set1-related proteins all found within COMPASS-like compositions capable of methylating histone H3K4. Furthermore, given that there is almost no sequence homology between many of the MLL translocation partners, for many years, it was unclear why MLL translocations into so many unrelated genes result in the pathogenesis of leukemia. Our biochemical studies on the purification of the MLL-chimeras demonstrated that many of the MLL translocation partners are part of the same macromolecular complex we named the Super Elongation Complex (SEC). We demonstrated that the translocations of MLL within any of the subunits of SEC subunits result in the misrecruitment of SEC to the MLL target genes and in the perturbation of the transcriptional checkpoint control of these genes, triggering leukemic growth. Additionally, the recent cataloging of somatic mutations in cancer identified a large number of mutations in the components of the MLL1-4 and Set1A/B complexes in both hematological malignancies and solid tumors. However, we know very little why the COMPASS family is mutated in different cancers. Given that we have developed a fantastic set of reagents and tools over the past seventeen years towards these factors and their associated proteins, chromatin, and other chromatin modifiers in multiple model systems; my laboratory is in a very unique position to define the molecular bases of these factors' involvement in cancer pathogenesis for the purpose of targeted therapeutics. Therefore, the goals of this R35 application is the full molecular and biochemical characterization of the COMPASS family, the translocation partners within the Super Elongation Complex (SEC), and the role of chromatin itself in the regulation of gene expression and development, and how their mutations contribute to the pathogenesis of human cancer.