Role of Collaborator Proteins in Hoxa9-Mediated Leukemogenesis

协作蛋白在 Hoxa9 介导的白血病发生中的作用

• 批准号: 8551379
• 负责人: Cailin Terese Collins
• 金额: $ 3.58万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8551379
• 关键词: Accounting; Acute Myelocytic Leukemia; Acute leukemia; Address; Animals; Binding; Binding Sites; Biological Models; CCAAT-Enhancer-Binding Proteins; CDX2 gene; Catalytic Domain; Cell Differentiation process; Cell Line; Cell Lineage; Cells; Chromatin Structure; Complex; DNA Binding; Data; Development; Disease; Dissociation; Enhancers; Epigenetic Process; Event; Family; Figs - dietary; Gene Expression; Gene Expression Regulation; Goals; HOXA9 gene; Hematopoiesis; Hematopoietic; Hematopoietic stem cells; Human; Lead; Leukemic Cell; Link; Lymphoid; MEIS1 gene; Malignant lymphoid neoplasm; Mass Spectrum Analysis; Mediating; Modeling; Modification; Molecular; Mutate; Mutation; Myelogenous; Myeloid Leukemia; Myeloproliferative disease; NPM1 gene; NUP98 gene; Outcome; Pathogenesis; Play; Protein Binding; Protein Family; Proteins; Regulation; Research; Role; Signal Pathway; Site; Specificity; Subgroup; Transcriptional Regulation; Transplantation; Up-Regulation; Ursidae Family; Work; base; cell growth; cell transformation; chromatin remodeling; cofactor; genome-wide; homeodomain; improved; in vivo; insight; leukemia; leukemogenesis; member; nucleophosmin; outcome forecast; overexpression; progenitor; research study; response; therapeutic target; transcription factor

DESCRIPTION (provided by applicant): Hoxa9 is a homeodomain containing transcription factor that plays a key role in hematopoietic stem cell expansion and is commonly deregulated in human acute leukemias. More than 50% of acute myeloid leukemia (AML) cases show overexpression of Hoxa9, almost always in association with overexpression of its cofactor Meis1. In a study of gene expression in human AMLs, high expression HOXA9 was the single most predictive mark for poor prognosis. A wide range of data suggests that Hoxa9 and Meis1 play a synergistic causative role in AML, though the molecular mechanisms leading to transformation by Hoxa9 and Meis1 remain elusive. Understanding Hoxa9-mediated leukemogenesis first requires a better understanding of what confers binding specificity of Hox family proteins. All Hox proteins bind the ubiquitous TAAT motif through their highly homologous homeodomains, which alone cannot account for their tight control of transcriptional activity. Additional sequence specificity is achieved in vivo through association with other DNA-binding cofactors, such as Meis1. Another level of regulation is likely conferred by diverse sets of collaborators that direct Hox protein specificity, but the identity of these proteins and the mechanisms through which they regulate Hox binding have yet to be elucidated. We have made considerable progress towards determining potential collaborators by characterizing in vivo binding sites of Hoxa9 and Meis1 and by identifying proteins that interact with the Hoxa9 complex. We found that Hoxa9 and Meis1 bind to evolutionarily conserved sites that contain an epigenetic signature consistent with enhancer sequences. De novo motif analysis of the binding regions showed a marked enrichment of motifs for transcription factors (TF) in the C/EBP, ETS, and STAT families. Subsequent mass spectrometry and coimmunoprecipitation experiments have confirmed association of the Hoxa9 complex with C/ebp a and Stat5. We have recently generated leukemic cell line model systems that conditionally express C/ebp a, Pu.1 and Stat5, and we will use these cells to study the role of each protein in targeting Hoxa9 to specific binding sites in myeloid and lymphoid lineages. We will also use these models to determine the effect of C/ebp a, Pu.1 and Stat5 on the transcriptional activity of Hoxa9. Finally, we will use a cell line we have established with conditional expression of the chromatin remodeler, Brg1, to determine the functional relationship between Brg1 and C/ebp a in modulating Hoxa9 complex activity. Together these studies will provide many new mechanistic insights into leukemogenesis mediated by high-level Hoxa9 expression. )

描述（由申请人提供）：Hoxa 9是一种含有同源结构域的转录因子，其在造血干细胞扩增中起关键作用，并且通常在人急性白血病中失调。超过50%的急性髓性白血病（AML）病例显示Hoxa 9过表达，几乎总是与其辅因子Meis 1过表达相关。在一项人类AML基因表达的研究中，高表达HOXA 9是预后不良的唯一最具预测性的标志。广泛的数据表明，Hoxa 9和Meis 1在AML中发挥协同致病作用，尽管导致Hoxa 9和Meis 1转化的分子机制仍然难以捉摸。 理解Hoxa 9介导的白血病发生首先需要更好地理解是什么赋予Hox家族蛋白的结合特异性。所有的Hox蛋白通过其高度同源的同源结构域结合普遍存在的TAAT基序，这不能单独解释它们对转录活性的严格控制。 通过与其他DNA结合辅因子（如Meis 1）结合，可在体内实现额外的序列特异性。另一个水平的调节可能是由指导Hox蛋白特异性的不同合作者赋予的，但是这些蛋白的身份以及它们调节Hox结合的机制尚未阐明。通过表征Hoxa 9和Meis 1的体内结合位点以及鉴定与Hoxa 9复合物相互作用的蛋白质，我们在确定潜在合作者方面取得了相当大的进展。我们发现，Hoxa 9和Meis 1结合到进化上保守的位点，这些位点包含与增强子序列一致的表观遗传特征。从头结合区的基序分析表明，在C/EBP，ETS和STAT家族的转录因子（TF）的基序显着富集。随后的质谱和免疫共沉淀实验证实了Hoxa 9复合物与C/ebpa和Stat 5的结合。我们最近已经产生了条件性表达C/ebpa、Pu.1和Stat 5的白血病细胞系模型系统，并且我们将使用这些细胞来研究每种蛋白质在将Hoxa 9靶向至骨髓和淋巴谱系中的特异性结合位点中的作用。我们还将使用这些模型来确定C/ebpa、Pu.1和Stat 5对Hoxa 9转录活性的影响。最后，我们将使用我们已经建立的染色质重塑剂Brg 1的条件表达的细胞系，以确定Brg 1和C/ebpa在调节Hoxa 9复合物活性中的功能关系。这些研究将为高水平Hoxa 9表达介导的白血病发生提供许多新的机制见解。)