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: 8394574
• 负责人: Cailin Terese Collins
• 金额: $ 3.27万
• 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/8394574
• 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. ) PUBLIC HEALTH RELEVANCE: Human acute myeloid leukemia (AML) is a highly heterogeneous disease that varies significantly in prognosis and response to treatment. Understanding the molecular basis behind leukemic transformation in different subgroups will be crucial for development of targeted therapeutics needed to improve survival and outcomes. Our research will investigate the molecular mechanisms important in AML with high levels of Hoxa9 expression, a transcription factor that is upregulated in 50% of AML cases and is associated with poor prognosis.

描述(申请人提供)：Hoxa9是一种含有转录因子的同源结构域，在造血干细胞扩增中发挥关键作用，在人类急性白血病中通常被解除调控。超过50%的急性髓系白血病(AML)患者存在Hoxa9的过度表达，几乎总是与其辅助因子Meis1的过度表达有关。在一项对人类AML基因表达的研究中，HOXA9的高表达是预后不良的唯一最具预测性的标志。大量数据表明，Hoxa9和Meis1在AML中起协同致病作用，但导致Hoxa9和Meis1转化的分子机制仍不清楚。理解Hoxa9介导的白血病发生首先需要更好地理解是什么赋予了HOX家族蛋白的结合特异性。所有的Hox蛋白都通过它们高度同源的同源结构域与无处不在的Taat基序结合，这本身不能解释它们对转录活性的严格控制。在体内，通过与其他DNA结合辅助因子(如Meis1)的结合，实现了额外的序列特异性。另一种水平的调控可能是由不同的合作者授予的，指导HOX蛋白的特异性，但这些蛋白的身份和它们调控HOX结合的机制尚未阐明。我们通过鉴定Hoxa9和Meis1的体内结合位点和鉴定与Hoxa9复合体相互作用的蛋白质，在确定潜在合作者方面取得了相当大的进展。我们发现Hoxa9和Meis1与进化上保守的位点结合，这些位点包含与增强子序列一致的表观遗传特征。对结合区的从头分析表明，C/EBP、Ets和STAT家族中转录因子(Tf)的基序显著丰富。随后的质谱学和免疫共沉淀实验证实了Hoxa9复合体与C/eBP a和Stat5的联系。我们最近建立了有条件地表达C/eBP a、PU.1和Stat5的白血病细胞系模型系统，我们将使用这些细胞来研究每种蛋白在将Hoxa9靶向髓系和淋巴系中特定结合部位方面的作用。我们还将使用这些模型来确定C/eBP a、PU.1和Stat5对Hoxa9转录活性的影响。最后，我们将使用我们建立的染色质重构体BRG1的条件表达细胞系来确定BRG1和C/eBP a在调节Hoxa9复合体活性中的功能关系。总之，这些研究将为Hoxa9高水平表达介导的白血病发生提供许多新的机制见解。) 公共卫生相关性：人类急性髓系白血病(AML)是一种高度异质性的疾病，其预后和治疗反应差异很大。了解不同亚群白血病转化背后的分子基础，对于开发提高存活率和预后所需的靶向治疗至关重要。我们的研究将探讨Hoxa9高水平表达在AML中的重要分子机制，Hoxa9是一种转录因子，在50%的AML病例中上调，并与不良预后相关。