Epigenetic Mechanisms and Targeting in MLL Leukemia

项目总结/摘要 MLL是一种表观遗传调节蛋白，在预后不良的白血病亚群中发生突变 治疗选择也很少MLL白血病的表观遗传学通路及其干扰 发病机制复杂，靶向分子治疗的有效性尚未建立。的 这项更新申请中提出的研究调查了ASH 1 L的病理作用， 表观遗传调节因子以前没有牵连在MLL白血病，并将其定义为一个作用， 潜在的治疗靶点。 大量的初步数据表明，MLL在参与白血病发生的靶基因上的募集 依赖于ASH 1 L，ASH 1 L是一种组蛋白甲基转移酶，其特异性地使赖氨酸上的组蛋白H3二甲基化 36（H3 K36 me 2）与活性启动子相关。此外，白血病需要ASH 1 L MLL癌蛋白在急性髓性白血病小鼠模型中的转化。的组件 MLL复合物（LEDGF）特异性结合H3 K36 me 2，表明ASH 1 L可能是H3 K36 me 2的关键上游调控因子。 MLL在其靶基因处的募集或保留的作用。然而，所涉及的具体机制 对人类白血病的影响仍有待确定。拟议的研究将涉及 假设ASH 1 L在MLL致癌途径中起关键作用， 在特异性靶启动子处富含H3 K36二甲基的染色质环境，以促进H3 K36二甲基与细胞的结合。 一种干扰白血病细胞基因表达的MLL蛋白复合物。 第一个具体目标的研究将建立ASH 1 L和组蛋白H3 K36双链的功能作用， 利用shRNA技术在临床前和人类MLL白血病发病机制中的甲基化 白血病细胞模型系统。这些研究将确定哪些白血病亚型依赖于 ASH 1 L，并表征其抑制的有害后果，为合理的 白血病的治疗策略 第二个目标的研究将使用染色质免疫沉淀技术来建立基因组- 广泛分布的组蛋白修饰，决定哪些标志物和因子是选择性依赖于 ASH 1 L，并建立各自的机制作用，在定义所需的表观基因组状态 MLL白血病细胞基因表达异常。 第三个具体目标的研究将采用结构-功能和无偏见的蛋白质组学方法， 表征将其活性导向白血病染色质的ASH 1 L异源相互作用- 相关靶基因。总的来说，拟议的研究将提供重要的见解， 白血病细胞中一种新的表观遗传调控途径的分子机制，并促进 专门针对该途径，以实现更有效的治疗。

Project Summary/Abstract MLL is an epigenetic regulatory protein that is mutated in a subset of leukemias with a poor prognosis and few therapeutic options. The epigenetic pathways and perturbations involved in MLL leukemia pathogenesis are complex, and the effectiveness of targeted molecular therapies not yet established. The studies proposed in this renewal application investigate the pathologic contributions of ASH1L, an epigenetic regulatory factor not previously implicated in MLL leukemia, and will define its role as a potential therapeutic target. Substantial preliminary data show that recruitment of MLL at target genes involved in leukemogenesis is dependent on ASH1L, a histone methyltransferase that specifically di-methylates histone H3 on lysine 36 (H3K36me2) associated with active promoters. Furthermore, ASH1L is required for leukemic transformation by MLL oncoproteins in mouse models of acute myeloid leukemia. A component of the MLL complex (LEDGF) specifically binds H3K36me2 suggesting that ASH1L may serve a key upstream role for recruitment or retention of MLL at its target genes. However, the specific mechanisms involved and the consequences for human leukemia remain to be determined. The proposed studies will address the hypothesis that ASH1L serves a crucial role in the MLL oncogenic pathway by establishing a chromatin environment enriched for H3K36 di-methyl at specific target promoters to facilitate binding of the MLL protein complex that perturbs gene expression in leukemia cells. Studies in the first specific aim will establish the functional roles of ASH1L and histone H3K36 di- methylation in the pathogenesis of MLL leukemia using shRNA technology in pre-clinical and human leukemia cell model systems. These studies will define which leukemia subtypes are dependent on ASH1L, and characterize the deleterious consequences of its inhibition to provide the basis for a rational therapeutic strategy in leukemia. Studies in the second aim will use chromatin immunoprecipitation techniques to establish the genome- wide distribution of histone modifications, determine which marks and factors are selectively dependent on ASH1L, and establish their respective mechanistic roles in defining the epigenomic states required for aberrant gene expression in MLL leukemia cells. Studies in the third specific aim will employ structure-function and unbiased proteomics approaches to characterize ASH1L heterologous interactions that direct its activity to the chromatin of leukemia- associated target genes. Taken together, the proposed studies will provide significant insights into the molecular mechanisms of a novel epigenetic regulatory pathway in leukemia cells, and facilitate efforts to specifically target the pathway to achieve more efficacious therapies.