Regulation of RUNX1 Multiprotein Complex Formation during Hematopoiesis

描述（由申请人提供）：转录因子RUNX 1在永久性造血干细胞（HSC）个体发育、HSC维持、巨核细胞（Mk）成熟和淋巴细胞分化中起重要作用。RUNX 1缺陷导致HSC和祖细胞的不平衡，并且是高达30%的所有人类白血病的早期起始步骤。RUNX 1也是高危骨髓增生异常综合征（MDS）杂合失活突变的复发靶点。尽管RUNX 1在正常和恶性人类造血中发挥着重要作用，但其调控机制仍不完全清楚。这种知识上的差距阻碍了将RUNX 1作为治疗靶点的努力。我们研究的长期目标是阐明这些机制，并将其转化为新的治疗策略。我们之前的工作和该领域的其他人的工作表明，RUNX 1组装成调节其活性的大型动态多蛋白复合物。这些相互作用涉及其他转录因子、表观遗传调节因子和信号传导酶。我们假设这些相互作用是由细胞信号通路调节的，并且这些通路的药理学操作可用于增强与部分RUNX 1缺陷相关的疾病中的残余RUNX 1活性。这是基于我们的初步研究，证明了src家族激酶（SFKs）对RUNX 1活性的稳态抑制，以及涉及MEK/ERK介导的磷酸化靶向区域的协同RUNX 1：Ets转录因子相互作用。本研究的主要目的是：（1）鉴定细胞成熟过程中RUNX 1多蛋白复合物形成的变化，并将其与RUNX 1活性联系起来;（2）确定SFK和ERK信号通路如何调节RUNX 1与染色质重塑复合物/转录因子的相互作用，以及它们如何影响RUNX 1靶基因的表达;（3）探索残余RUNX 1活性的药理学增强是否可以减轻在RUNX 1显性阴性融合分子的小鼠模型中观察到的部分RUNX 1缺陷和影响白血病发生的HSC/祖细胞失衡。这些研究的结果应该填补了关于正常RUNX 1调节机制的知识的重要空白，并使RUNX 1能够作为血液疾病的治疗靶点。这项工作有可能立即产生影响，因为我们假设影响RUNX 1活性的信号通路的小分子抑制剂已经在临床上可用和/或正在测试中。

DESCRIPTION (provided by applicant): The transcription factor RUNX1 plays essential roles in definitive hematopoietic stem cell (HSC) ontogeny, HSC maintenance, megakaryocyte (Mk) maturation, and lymphocyte differentiation. RUNX1 deficiency causes an imbalance of HSC and progenitor cells, and is an early initiating step in up to 30% of all human leukemias. RUNX1 is also a recurrent target of heterozygous inactivating mutations in high-risk myelodysplastic syndrome (MDS). Despite RUNX1's central role in normal and malignant human hematopoiesis, its regulatory mechanisms remain incompletely understood. This gap in knowledge has impeded efforts to exploit RUNX1 as a therapeutic target. The long-term goal of our research is to elucidate these mechanisms and translate them into new treatment strategies. Our prior work and that of others in the field indicates that RUNX1 assembles into large dynamic multiprotein complexes that modulate its activity. These interactions involve other transcription factors, epigenetic regulators, and signaling enzymes. We hypothesize that these interactions are modulated by cell signaling pathways and that pharmacologic manipulation of these pathways can be used to enhance residual RUNX1 activity in disorders associated with partial RUNX1 deficiency. This is based on our preliminary studies demonstrating steady-state inhibition of RUNX1 activity by src-family kinases (SFKs), and synergistic RUNX1:Ets transcription factor interactions involving a region targeted by MEK/ERK-mediated phosphorylation. The following aims have been developed to test our central hypothesis: (1) identify changes in RUNX1 multiprotein complex formation that occur during cellular maturation and correlate them with RUNX1 activity; (2) determine how SFK and ERK signaling pathways modulate RUNX1 interactions with chromatin remodeling complexes/transcription factors and how they affect RUNX1 target gene expression; (3) Explore whether pharmacologic enhancement of residual RUNX1 activity can alleviate the HSC/progenitor cell imbalance observed with partial RUNX1 deficiency and impact leukemogenesis in mouse models of RUNX1 dominant negative fusion molecules. The results of these studies should fill in important gaps in knowledge regarding normal RUNX1 regulatory mechanisms and enable exploitation of RUNX1 as a therapeutic target in hematologic disorders. This work has the potential for immediate impact, as small molecule inhibitors of signaling pathways we hypothesize to impact RUNX1 activity are already clinically available and/or in testing.