MYC TRANSCRIPTION FACTOR NETWORK IN STEM CELL BIOLOGY

造血干细胞的谱系定型、分化和自我更新可能涉及调控转录因子控制下基因表达模式的特异性变化。这些改变的基因表达模式不仅在产生细胞类型特异性蛋白质方面很重要，而且在确定细胞是否以及何时继续增殖或退出细胞周期方面也很重要。Myc转录因子已被证明在造血细胞的这一决定中发挥重要作用。早期的工作已经证明Myc作为相互作用蛋白网络的一部分发挥作用，所述相互作用蛋白网络包括Myc的专性二聚化伴侣Max以及其他Max相互作用蛋白，包括Mad家族的转录抑制因子。已知Myc网络参与增殖、分化、细胞凋亡和肿瘤形成。在上一个资助期的工作已经指出了Mad在造血细胞分化中的作用，并导致了对Myc功能的更好理解。在本申请中，我们建议扩展这些研究，以阐明这些蛋白质在造血细胞中的功能。在特定目的1和2中，我们计划采用靶向缺失以及造血细胞中的转基因。在特定目的1和2中，我们计划采用靶向缺失以及转基因表达或鼠mad家族基因来研究体内造血。在目的1中，我们提出了Myc和Mad转录活性在造血发育中的作用，通过检查它们在已知的控制淋巴细胞生成的信号通路的背景下的活动来分析。这些研究的结果将用于目标2，以指导实验中的作用，Mad的调节造血干细胞池的大小，生长因子的敏感性，和谱系承诺。在具体目标3中，我们将使用寡核苷酸微阵列分析来识别造血细胞中由Myc和Mad差异调节的基因。由于Myc和Mad蛋白似乎通过改变组蛋白乙酰化来调节转录，因此这项工作将有助于将造血分化与基因表达和染色质结构的特定变化相关联。

Lineage commitment, differentiation, and self-renewal of hematopoietic stem cells are likely to involve specific changes in patterns of gene expression under the control of regulatory transcription factors. These altered patterns of gene expression are important, not only in producing cell-type specific proteins, but also in determining if, and when, cells continue to proliferative or to exit the cell cycle. The Myc transcription factor has been shown to play an important role in this decision in hematopoietic cells. Earlier work has demonstrated that Myc functions as part of a network of interacting proteins which include Myc's obligate dimerization partner, Max, as well as other Max interacting proteins, including the Mad family of transcriptional repressors. The Myc network is known to be involved in proliferation, differentiation, apoptosis and neoplasia. Work during the previous grant period has pointed to a role for Mad in hematopoietic cell differentiation and has led to a better understanding of the function of Myc. In this application we propose to extend these studies in order to elucidate the function of these proteins in hematopoietic cells. In Specific Aims 1 and 2 we plan to employ targeted deletions, as well transgenic in hematopoietic cells. In Specific Aims 1 and 2 we plan to employ targeted deletions, as well transgenic expression, or murine mad family genes to study hematopoiesis in vivo. In Aim 1 we propose to analyze the role of Myc and Mad transcriptional activities in hematopoietic development by examining their activities in the context of the known signaling pathways that control lymphopoiesis. The results of these studies will be used in Aim 2 to guide experiments on the role of Mad in the regulation of hematopoietic stem cell pool size, growth factor sensitivity, and lineage commitment. In Specific Aim 3 we will use oligonucleotide microarray analysis to identify genes differentially regulated by Myc and Mad in hematopoietic cells. Because Myc and Mad proteins appear to regulate transcription through alterations in histone acetylation, this work will help correlate hematopoietic differentiation with specific changes in gene expression and chromatin structure.