EPIGENETIC REGULATION TISSUE-SPECIFIC GENE TRANSCRIPTION

描述（由申请人提供）： 造血涉及基因表达的复杂模式，其在早期前体细胞中编程为完全分化的细胞类型，并且整个途径代表组织特异性基因表达的复杂实例。哺乳动物基因表达的组织特异性由反式作用因子的水平以及允许发育所需的长期控制和灵活性的表观遗传事件决定。哺乳动物基因表达的复杂性是通过一系列机制从人类和小鼠基因组中有限数量（约28，000个）的基因中实现的，这些机制通常导致在分化的不同阶段中在严格控制下从单个基因产生几种转录物。我们一直在研究小鼠的fpgs基因，作为一个遗传位点的例子，其中两个不同的基因产物由两个相距较远的启动子以组织特异性模式产生。该基因特别有趣，因为任何给定的组织仅从一个启动子产生转录物，尽管从一个或另一个或两个都不表达的组织是已知的。我们对小鼠fpgs基因的研究表明，这两个启动子之间存在着多层次的协调控制，但是这两个启动子的事件遵循着非常不同的模式。我的初步研究最近表明，该基因构成了内源性基因中转录干扰的极少数已知例子之一，也是少数组织特异性沉默与正常组织中CpG稀疏启动子处的DNA甲基化相关的启动子之一。这些研究还提出了一个基本的重要观点，即转录起始复合物在产生成熟转录物的组织和不产生可检测转录物的组织中至少在一些启动子上保持平衡。这个建议的重点是探讨DNA甲基化和转录干扰如何有助于启动子选择在小鼠fpgs基因在组织特异性的方式，并确定是否和在何种程度上，我们看到的现象整合控制在这个单一的两个启动子基因捕获一般趋势，在控制整个小鼠基因组的基因表达。人类生物学的一个核心方面是对单个受精细胞中存在的信息进行编程，该受精细胞编码成年人每个细胞中表达的蛋白质。这种组织特异性的表达模式在血细胞发育过程中表现得最为明显。在这个应用程序中，我建议研究如何修改DNA和一类DMA结合蛋白（组蛋白）指导这种组织特异性的信息流和记忆。

DESCRIPTION (provided by applicant): Hematopoiesis involves an intricate pattern of gene expression that is programmed in early precursor cells to fully differentiated cell types, and the whole pathway represents an intricate example of tissue specific gene expression. The tissue specificity of mammalian gene expression is determined by the levels of trans-acting factors, as well as by epigenetic events that allow both the long-term control and the flexibility required by development. The complexity of mammalian gene expression is realized from the limited number (ca 28,000) of genes in human and mouse genomes by a series of mechanisms that often results in the production of several transcripts from a single gene under tight control in different stages of differentiation. We have been studying the mouse folylpolyglutamate synthetase (fpgs) gene as an example of a genetic locus in which two distinct gene products are produced from two distantly placed promoters in a tissue-specific pattern. This gene is particularly interesting because any given tissue produces transcript from only one promoter, although tissues that express from the one or the other or neither are known. Our studies on the mouse fpgs gene have indicated that there are layers of coordinated control of the two promoters, but that events at the two promoters follow very different patterns. My initial studies have recently shown that this gene constitutes one of the very few known examples of transcriptional interference in an endogenous gene, and also one of the few promoters for which tissue-specific silencing correlates with DNA methylation at a CpG-sparse promoter in normal tissues. These studies have also raised the fundamentally important point that transcriptional initiation complexes are poised over at least some promoters both in tissues that produce a mature transcript and in those which do not produce detectable transcript. The focus of this proposal is to explore how DNA methylation and transcriptional interference contribute to promoter choice at the mouse fpgs gene in a tissue-specific fashion, and to determine whether and the extent to which the phenomena we see integrating control at this single two promoter gene capture general trends in control of gene expression across the mouse genome. A central aspect of human biology is the programming of information present in a single fertilized cell that encodes what proteins are expressed in every cell in the adult human being. Such a tissue-specific expression pattern is seen nowhere as clearly as in the development of the blood cells. In this application, I propose to study how modification of DNA and of a class of DMA-bound proteins (histones) directs this tissue specific information flow and memory.