Regulation of RUNX1 Multiprotein Complex Formation during Hematopoiesis

描述(由申请人提供)：转录因子RUNX1在确定的造血干细胞(HSC)个体发育、HSC维持、巨核细胞(Mk)成熟和淋巴细胞分化中发挥重要作用。RUNX1缺乏导致HSC和祖细胞的失衡，是高达30%的人类白血病的早期启动步骤。RUNX1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RUNX1的S在正常和恶性的人类造血中起着核心作用，但其调控机制仍不完全清楚。这种知识上的差距阻碍了将RUNX1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其他人的工作表明，RUNX1组装成大型动态多蛋白复合体，调节其活性。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酶。我们假设这些相互作用是由细胞信号通路调节的，这些通路的药理操作可以用来增强与部分RUNX1缺乏相关的疾病中残留的RUNX1活性。这是基于我们的初步研究，证明了src家族激酶(SFK)对RUNX1活性的稳态抑制，以及涉及MEK/ERK介导的磷酸化靶向的区域的协同RUNX1：ETS转录因子相互作用。现已确定我们的中心假设：(1)确定在细胞成熟过程中发生的RUNX1多蛋白复合体形成的变化，并将它们与RUNX1活性相关联；(2)确定SFK和ERK信号通路如何调节RUNX1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RUNX1靶基因的表达；(3)探讨以药理方法增强残留的RUNX1活性是否能缓解因部分RUNX1缺乏而观察到的HSC/祖细胞失衡，从而影响RUNX1阴性融合分子小鼠的白血病发生。这些研究的结果应该会填补有关正常RUNX1调节机制的知识的重要空白，并使RUNX1能够作为血液病的治疗靶点。这项工作有可能产生立竿见影的效果，因为我们假设影响RUNX1活性的信号通路的小分子抑制剂已经在临床上使用和/或在测试中。

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.