GABP-controlled gene regulatory network in T lymphocytes

描述（由申请人提供）：针对外来抗原的保护性细胞免疫应答依赖于功能性T淋巴细胞。T细胞的发育、激活和分化受转录因子的不同组合控制。GA结合蛋白（GABP）是一种普遍表达的Ets家族转录因子，功能性GABP由两个不同的亚基GABP1和GABP2组成，分别介导DNA结合和反激活。先前我们已经证明，GABP对T细胞中白细胞介素-7受体1 （IL-7R1）链的表达具有关键调节作用，这表明GABP在免疫系统中起关键作用。鉴于GABP1基因的完全失活会导致着床前的死亡，我们已经产生了一种GABP1突变小鼠品系，它是次胚性的，并且在胚胎发生期间延长了存活时间。在我们的初步研究中，使用GABP1突变胚胎的胎儿肝细胞重建rag2缺陷小鼠的淋巴细胞室，我们发现GABP在胸腺细胞发育和T细胞介导的免疫应答中起重要作用。

DESCRIPTION (provided by applicant): Protective cellular immune responses against foreign antigens rely on functional T lymphocytes. The development, activation and differentiation of T cells are controlled by transcription factors in different combinations. GA binding protein (GABP) is a ubiquitously expressed Ets family transcription factor, and functional GABP consists of two different subunits, GABP1 and GABP2, which mediate DNA binding and transactivation, respectively. Previously we have demonstrated that GABP critically regulates the expression of interleukin-7 receptor 1 (IL-7R1) chain in T cells, suggesting a key role of GABP in the immune system. Whereas complete inactivation of the GABP1 gene caused pre- implantation lethality, we have generated a GABP1 mutant mouse strain that is hypomorphic and has prolonged survival during embryogenesis. In our preliminary studies using fetal liver cells from the GABP1 mutant embryos to reconstitute lymphoid compartment in Rag2-deficient mice, we found that GABP has essential roles in thymocyte development and T cell-mediated immune responses. This research project aims to construct a hierarchical and interactive gene regulatory network under the control of GABP in T cells. Our long-term goal is to elucidate how GABP programs T lymphopoiesis and T cell immune responses through regulating its target genes and interacting with other key factors. This information will provide a scientific basis for modulating outcomes of hematopoietic stem cell differentiation and immune responses under physiological and pathological conditions. Specific Aim. To identify direct GABP target genes in T lymphocytes and to establish a GABP- controlled gene regulatory network programming T cell biology. Taking advantage of our GeneChip microarray analysis data, we will extend our studies to identify GABP direct target genes using approaches of comparative genomics and chromatin immunoprecipitation assay (ChIP) coupled with a mouse promoter array (ChIP-on-chip). We will then map the precise locations of GABP-binding elements and investigate their functional importance in activating/repressing respective genes. With this knowledge, a gene regulatory network in T cells can be constructed, and this will provide a platform for a broader investigation of the interactive transcriptional control of thymocyte development and T cell functions. Reconstitution of the immune system in individuals with inherited and acquired immunodeficiency remains a major challenge, and a better understanding of the molecular mechanism by which hematopoietic stem cells differentiate to lymphoid lineages is fundamental to improve strategies for immune system reconstitution. This project will generate insights into how GABP, a transcription factor, contributes to specifying hematopoietic stem cells to the T-lineage cells, and how GABP modulates the cellular immune response. This knowledge will provide a scientific basis for manipulating outcomes of hematopoietic stem cell differentiation and immune response under physiological and pathological conditions.