EPIGENETIC REGULATION TISSUE-SPECIFIC GENE TRANSCRIPTION

描述(由申请人提供)： 造血涉及一种复杂的基因表达模式，这种模式在早期的前体细胞中被编程为完全分化的细胞类型，整个途径代表了组织特异性基因表达的复杂例子。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长期控制和发育所需的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从人类和小鼠基因组中有限的基因数量(约28,000个)通过一系列机制实现的，这些机制往往导致在分化的不同阶段严格控制单个基因产生几个转录本。我们一直在研究小鼠叶多谷氨酸合成酶(Fpgs)基因，作为一个遗传位点的例子，在这个遗传位点中，两个不同的基因产物是由两个相距较远的启动子以组织特有的模式产生的。这种基因特别有趣，因为任何给定的组织只产生一个启动子的转录本，尽管表达其中一个或另一个或两者都不表达的组织是已知的。我们对小鼠fpgs基因的研究表明，这两个启动子存在多层协调控制，但两个启动子的活动遵循非常不同的模式。我最近的初步研究表明，该基因是已知的极少数内源性基因转录干扰的例子之一，也是正常组织中组织特异性沉默与CpG稀疏启动子DNA甲基化相关的少数启动子之一。这些研究还提出了一个根本重要的观点，即转录起始复合体在产生成熟转录本的组织和不产生可检测转录本的组织中都稳定在至少一些启动子上。这项建议的重点是探索DNA甲基化和转录干扰如何以组织特异性的方式促进小鼠fpgs基因的启动子选择，并确定我们在这个单一的两个启动子基因上整合控制的现象是否以及在多大程度上捕获了整个小鼠基因组中基因表达控制的一般趋势。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，这些信息编码了成年人类每个细胞中表达的蛋白质。这种特定于组织的表达模式在血细胞的发育过程中表现得最为明显。在这个应用中，我打算研究DNA和一类DMA结合蛋白(组蛋白)的修饰如何引导这种组织特有的信息流和记忆。

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.