THE STRUCTURAL BASIS FOR THE ASSEMBLY AND REGULATION OF THE MLL CORE COMPLEX

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 混合血统白血病(MLL)蛋白催化组蛋白H3赖氨酸4(H3K4)甲基化，是调节HOX基因在造血和发育过程中必不可少的表观遗传标记。破坏MLL基因的易位存在于一组独特的急性白血病中，通常预示着预后不良。其他MLL重排和扩增可增强MLL？？S的酶活性，并具有致癌作用。MLL含有一个进化保守的~130个氨基酸SET结构域，催化H3K4甲基化。最近的研究表明，MLL的酶活性是由WDR5、RbBP5和ASH2 L等蛋白质组成的保守复合体调节的。这些蛋白质形成一个独立的复合体，与MLL结合并调节MLL？“S对H3K4单甲基化、二甲基化或三甲基化的能力，这种现象称为产品特异性”。由于不同水平的H3K4甲基化与不同的转录结果相关，了解MLL产物特异性调节的分子机制是非常必要的。尽管MLL具有重要的生物学作用及其与人类白血病的关系，但目前对MLL酶活性的蛋白质结构特征知之甚少。本研究的长期目标是充分表征MLL的组蛋白甲基转移酶活性，以便于识别和合理设计用于治疗人类白血病的新的抗癌药物。该建议采用结构-功能的方法来研究蛋白质-蛋白质相互作用调节MLL SET结构域的分子机制。我们已经绘制了MLL与WDR5相互作用的位置，并获得了WDR5与MLL衍生的多肽的晶体。其初始结构衍射值为1.72埃，并确定了多肽的结合部位。对于这项研究，我们希望获得更高分辨率的数据和更长的多肽，以确定MLL和WDR5之间的其他相互作用是否重要。在一个无关的项目中，我们最近还获得了一种胰岛素-维生素B12加合物的晶体，它为糖尿病的胰岛素治疗提供了一种潜在的口服替代品。虽然我们还没有对它们进行衍射测试(我们没有室内衍射仪)，但我们已经确认这些晶体是蛋白质，胰岛素B12加合物在溶液中形成单体。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Mixed Lineage Leukemia (MLL) protein catalyzes histone H3 lysine 4 (H3K4) methylation, which is an epigenetic mark essential for the regulation of HOX genes in hematopoiesis and development. Translocations that disrupt the MLL gene are present in a unique group of acute leukemias, often predicting a poor prognosis. Other MLL rearrangements and amplifications increase MLL¿¿"s enzymatic activity and are oncogenic. MLL contains an evolutionarily conserved ~130 amino acid SET domain that catalyzes H3K4 methylation. Recent studies indicate that the enzymatic activity of MLL is regulated by a conserved complex of proteins including WDR5, RbBP5, and ASH2L. These proteins form an independent complex that binds to MLL and regulates MLL¿¿"s ability to mono-, di-, or trimethylate H3K4, a phenomenon known as ¿¿¿Product Specificity¿¿". Since different levels of methylation of H3K4 are associated with different transcriptional outcomes, it is imperative to understand the molecular mechanisms by which the product specificity of MLL is regulated. Despite the important biological role of MLL and its involvement in human leukemia, there is currently little information about the protein-structural features that are responsible for the enzymatic activity of MLL. The long-term goal of this research is to fully characterize the histone methyltransferase activity of MLL to facilitate the identification and rational design of new anti-cancer drugs for the treatment of human leukemias. This proposal takes a structure-function approach to investigate the molecular mechanisms of MLL SET domain regulation by protein-protein interactions. We have mapped the site of interaction between MLL and WDR5, and have obtained crystals of WDR5 with a peptide derived from MLL. The initial structure diffracted to 1.72 angstroms, and elucidtaed the peptide binding site. For this investigation, we would like to obtain higher resolution data with a longer peptide to determine if other interactions between MLL and WDR5 are important. For an unrelated project, we have also recently obtained crystals of an insulin-vitamin B12 adduct, which offers a potential oral alternative for insulin treatment for diabetes. While we have not tested them for diffraction yet (we don`t have an in house diffractometer), we have confirmed that the crystals are protein, and that the insulin B12 adduct forms monomers in solution.