GABP Transcription Factor in Myeloid Differentiation

描述(由申请人提供)：本提案的目标是全面描述转录因子GA结合蛋白(GABP)的作用。在髓系分化和基因表达方面。转录因子调节造血祖细胞向髓系细胞(粒细胞和单核细胞)的发育，而转录因子缺陷与急性髓系白血病有关。GABP是调节髓系基因的有限数量的转录因子之一。它是一个四聚体复合体，由两个不同的蛋白质组成：1)GABPalpha，一种与DNA结合的ETS因子；2)GABPbeta，一种与Notch相关的蛋白质，含有转录激活和多聚体结构域。GABP在转录上激活CD18(β2白细胞整合素)和其他髓系基因；它是维甲酸对CD18转录激活所必需的。当粒细胞和单核细胞分化时，表达具有特定转录激活特性的不同的GABPβ亚型；条件表达某些GABPβ亚型诱导粒细胞分化和特有的基因表达。该提案将检验这样一种假设，即GABP介导了粒细胞分化的另一种途径，并且在髓系分化过程中需要特定的GABPβ亚型。GABP与PU.1、Sp1、RARpha和p300协同激活CD18。这项建议将使用下拉试验、共免疫沉淀和染色质免疫沉淀来定义GABP与其他关键髓系转录因子和共激活剂的物理和功能相互作用。它将检验GABP参与增强体--一种调节髓系基因表达的多蛋白复合体--的假设。小鼠是由GABPalpha ETS结构域两侧的loxP重组位点产生的。在体内和体外，GABPalpha被有效地删除；在小鼠中，GABPalpha的纯合缺失会导致早期胚胎致命缺陷。选择性地破坏髓系细胞中的GABPalpha表明它们需要GABP来生存和/或分化。GABP的下游靶点可能解释了GABPalpha零细胞的细胞缺陷。该提案将检验粒细胞存活和/或分化需要GABP的假设，并将定义GABP驱动髓系细胞发育的机制。这些研究将全面展示GABP在髓系基因表达中的作用，并为调节髓系分化的转录因子和辅助激活子相互作用提供重要的新信息。

DESCRIPTION (provided by applicant): The goal of this proposal is to comprehensively characterize the role of the transcription factor, GA-Binding Protein (GABP). in myeloid differentiation and gene expression. Transcription factors regulate development of myeloid cells (granulocytes and monocytes) from hematopoietic progenitor cells, and defects in transcription factors are associated with acute myelogenous leukemia. GABP is 1 of a limited number of transcription factors that regulate myeloid genes. It is a tetrameric complex that consists of 2 distinct proteins: 1) GABPalpha, an ets factor which binds to DNA, and 2) GABPbeta, a Notch-related protein which contains transcription activation and multimerization domains. GABP transcriptionally activates CD 18 (beta2 leukocyte integrin) and other myeloid genes; it is required for transcriptional activation of CD18 in response to retinoic acid. As granulocytes and monocytes differentiate, distinct isoforms of GABPbeta with specific transcriptional activation properties are expressed; conditional expression some GABP beta isoforms induces granulocytic differentiation and characteristic gene expression. The proposal will test the hypothesis that GABP mediates an alternative pathway to granulocytic differentiation and that specific GABPbeta isoforms are required during myeloid differentiation. GABP cooperates with PU.1, Sp1, RARalpha, and p300 to activate CD18. This proposal will use pull-down assays, co-immunoprecipitation, and chromatin immunoprecipitation to define the physical and functional interactions of GABP with other key myeloid transcription factors and co-activators. It will test the hypothesis that GABP participates in an enhanceosome - a multiprotein complex that regulates myeloid gene expression. Mice were generated with loxP recombination sites that flank the GABPalpha ets domain. GABPalpha is efficiently deleted in vivo and in vitro; homozygous deletion of GABPalpha in mice causes an early embryonic lethal defect. Selective disruption of GABPalpha in myeloid cells indicates that they require GABP for survival and/or differentiation. Downstream targets of GABP that may account for cellular defects of GABPalpha null cells have been identified. The proposal will test the hypothesis that GABP is required for granulocytic survival and/or differentiation and it will define mechanisms by which GABP drives myeloid cell development. These studies will provide a comprehensive demonstration of the role of GABP in myeloid gene expression and provide important new information regarding transcription factor and co-activator interactions that regulate myeloid differentiation.