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的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 混合谱系白血病（MLL）蛋白催化组蛋白H3赖氨酸4（H3 K4）甲基化，这是造血和发育中HOX基因调控所必需的表观遗传标记。破坏MLL基因的易位存在于一组独特的急性白血病中，通常预测预后不良。 其他MLL重排和扩增增加MLL的酶活性，是致癌的。MLL含有一个进化上保守的约130个氨基酸的SET结构域，其催化H3 K4甲基化。 最近的研究表明，MLL的酶活性是由一个保守的蛋白质复合物，包括WDR 5，RbBP 5，和ASH 2L调节。这些蛋白质形成独立的复合物，与MLL结合并调节MLL对H3 K4进行单、双或三甲基化的能力，这种现象称为"产物特异性"。由于H3 K4的不同甲基化水平与不同的转录结果相关，因此必须了解MLL产物特异性调节的分子机制。尽管MLL的重要生物学作用及其在人类白血病中的参与，但目前关于负责MLL的酶活性的蛋白质结构特征的信息很少。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，以促进用于治疗人类白血病的新抗癌药物的鉴定和合理设计。 该提案采用结构-功能方法来研究MLL SET结构域通过蛋白质-蛋白质相互作用调节的分子机制。我们已经绘制了MLL和WDR 5之间的相互作用的网站，并已获得晶体的WDR 5与来自MLL的肽。初始结构衍射至1.72埃，并阐明了肽结合位点。对于本研究，我们希望获得更长肽的更高分辨率数据，以确定MLL和WDR 5之间的其他相互作用是否重要。 对于一个无关的项目，我们最近还获得了胰岛素-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（我们没有内部衍射仪），但我们已经证实晶体是蛋白质，并且胰岛素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.