Function and targeting of a stable transcription factor complex in leukemia

描述（由申请人提供）：转录因子在许多类型的癌症中起关键作用，但长期以来被认为是"不可用药的"，因为缺乏特定的活性位点，这些位点可以被代表大多数当前药物的小分子类型靶向。然而，使用短肽最近已成为一种有前途的策略，通过特定的蛋白质复合物的功能，因为不同的相互作用模式可能会赋予高度的选择性的肽靶向转录因子。在这个提议中，我们试图使用这种新的策略来靶向致白血病融合蛋白/转录因子，AML1-ETO，这是最常见的急性髓系白血病。我们发现，在白血病细胞中，AML1-ETO存在于一个稳定的蛋白复合物中，含有多种转录因子和辅因子。在该复合物中，二聚化的AML1-ETO直接与涉及造血谱系发育事件的常规转录激活因子E蛋白家族相互作用。我们还发现，AML1-ETO二聚化结构域（NHR2），以前被证明是白血病的关键，利用二聚化α-螺旋的独特表面介导的AML1-ETO与E蛋白中的保守基序的相互作用。这种特殊的相互作用模式理想地允许设计抑制剂来特异性地破坏相互作用并操纵AML1-ETO的活性，从而为白血病治疗提供潜在的靶标。在这方面，并且为了进一步支持这种NHR2-E蛋白相互作用作为治疗靶标，已经显示破坏NHR2-E蛋白相互作用但不破坏NHR2二聚化的特定突变损害AML1-ETO增强人造血干细胞自我更新的能力。基于这些对AML1-ETO转录因子/辅因子复合物（AETFC）的生物化学和功能研究，我们计划（i）通过详细的机制研究进一步鉴定和表征AETFC复合物;（ii）通过全基因组ChIP分析鉴定直接AML1-ETO靶基因;（iii）通过基于细胞和无细胞的体外转录系统，阐明AML1-ETO和其他成分协同调节转录（去调节转录）的详细机制;（iv）研究（并验证）单个组分的生物学功能及其在白血病细胞和小鼠模型中的相互作用;以及（v）设计特异性拟肽抑制剂以操纵AML 1-ETO在转录和白血病发生中的作用。 公共卫生相关性：许多染色体易位导致白血病融合蛋白改变正常转录程序。这项研究将提供一个可能的不同功能和作用机制的白血病融合蛋白（AML1-ETO），是最常见的急性髓系白血病参与更深入的了解。这些信息，反过来，将被用来开发一种拟肽抑制剂，靶向这种白血病融合蛋白，并提供了一种新的治疗方法，相关的白血病。

DESCRIPTION (provided by applicant): Transcription factors play critical roles in many types of cancer but, for a long time, were considered "undruggable" because of the lack of specific active sites that can be targeted by the types of small molecules that typify most current drugs. However, the use of short peptides has recently emerged as a promising strategy to target transcription factors that function through specific protein complexes, since distinct interaction patterns may confer a high degree of selectivity on the peptide. In this proposal, we seek to use this new strategy to target the leukemogenic fusion protein/transcription factor, AML1-ETO, that is most frequently involved in acute myeloid leukemia. We have found that, in leukemic cells, AML1- ETO resides in a stable protein complex containing multiple transcription factors and cofactors. Within this complex, the dimerized AML1-ETO directly interacts with a family of conventional transcriptional activators, E proteins, that are implicated in hematopoietic lineage developmental events. We also have found that the AML1-ETO dimerization domain (NHR2), which previously was shown to be critical for leukemogenesis, utilizes a distinct surface of the dimerized alpha-helixes to mediate the AML1-ETO interaction with a conserved motif in E proteins. This particular interaction pattern ideally allows the design of inhibitors to specifically disrupt the interaction and to manipulate the activities of AML1-ETO, thus providing a potential target for leukemia treatment. In this regard, and in further support of this NHR2-E protein interaction as a therapeutic target, a specific mutation that disrupts the NHR2-E protein interaction, but not NHR2 dimerization, has been shown to impair the capacity of AML1-ETO to enhance human hematopoietic stem cell self-renewal. Based on these biochemical and functional studies of the AML1-ETO-containing transcription factor/cofactor (AETFC) complex(es), we plan (i) to further identify and characterize the AETFC complex(es) by detailed mechanistic studies; (ii) to identify direct AML1- ETO target genes by genome-wide ChIP analyses; (iii) to clarify, through cell-based and cell-free in vitro transcription systems, the detailed mechanisms by which AML1-ETO and other components cooperate to (de)regulate transcription; (iv) to study (and validate) the biological functions of individual components and their interactions in leukemic cellular and mouse models; and (v) to design specific peptidomimetic inhibitors to manipulate the action of AML1-ETO in transcription and leukemogenesis. PUBLIC HEALTH RELEVANCE: A number of chromosomal translocations result in leukemogenic fusion proteins that alter normal transcription programs. This study will provide a deeper understanding of the likely diverse functions and mechanisms of action of the leukemogenic fusion protein (AML1-ETO) that is most frequently involved in acute myeloid leukemia. This information, in turn, will be used to develop a peptidomimetic inhibitor that targets this leukemogenic fusion protein and offers a new therapeutic approach for related leukemias.