Epigenetic Mechanisms and Targeting in MLL Leukemia

项目摘要/摘要 MLL是一种表观遗传调节蛋白，在预后较差的白血病亚群中突变 而且几乎没有治疗选择。MLL白血病中涉及的表观遗传途径和扰动 发病机制复杂，靶向分子治疗的有效性尚未确立。这个 在这项更新申请中提出的研究调查了Ash1，And 表观遗传调节因子以前没有涉及MLL白血病，并将定义其作用为 潜在的治疗靶点。 大量的初步数据显示，MLL在参与白血病发生的靶基因上招募 依赖于组蛋白H3赖氨酸二甲基化的组蛋白甲基转移酶 36(H3K36me2)与活性启动子相关。此外，白血病需要使用Ash1 MLL癌蛋白在小鼠急性髓系白血病模型中的转化。中的一个组件 MLL复合体(LEDGF)与H3K36me2特异性结合，提示Ash1可能在上游发挥关键作用 在其靶基因上招募或保留MLL的作用。然而，涉及的具体机制 而对人类白血病的后果仍有待确定。拟议的研究将涉及 ASH11在MLL致癌途径中起关键作用的假说是通过建立一个 染色质环境富含H3K36二甲基的特定靶标启动子，以促进结合 干扰白血病细胞基因表达的MLL蛋白复合体。 第一个特定目标的研究将确定Ash1和组蛋白H3K36双亚基的功能作用。 应用shRNA技术研究临床前和人类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 并刻画了其抑制的有害后果，为理性的 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- 组蛋白修饰的广泛分布，决定了哪些标记和因子选择性地依赖于 Ash11，并确定它们各自在定义所需的表观基因组状态方面的机械性作用 MLL白血病细胞基因异常表达的研究 第三个特定目标的研究将使用结构-功能和无偏见的蛋白质组学方法 鉴定将其活性定向到白血病染色质的Ash11异源相互作用- 相关的靶基因。综上所述，拟议的研究将为 白血病细胞中新的表观遗传调控途径的分子机制，并促进努力 特别针对这一途径，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.