GLUCOSE SENSING AND SIGNALING IN YEAST

葡萄糖是酵母菌的首选碳源，就像大多数酵母菌一样。 哺乳动物细胞。这两种生物都进化出了复杂的 监管机制，以优化其利用。在酵母中，葡萄糖 抑制许多细胞生长所必需的基因的表达 葡萄糖(例如，半乳糖基因)，并诱导几个基因的表达 高效利用所必需的(例如，编码葡萄糖的HXT基因 转运体)；哺乳动物已经设计出多种机制来维持 葡萄糖动态平衡。我们相信，了解血糖检测和 简单真核生物烘焙酵母(Saccharmyces)中的信号机制 Cerevisiae)将通知分析较大的葡萄糖信号 真核细胞。 葡萄糖抑制和葡萄糖诱导对酵母基因表达的影响 可以被视为信号转导途径：细胞外葡萄糖是 由受体(可能是葡萄糖转运体)感知，产生一种 最终影响基因调控蛋白功能的信号。 这两条通路的基因调控蛋白都已被确定：Mig1p 抑制物是葡萄糖抑制途径的中心成分，并且 已经确定了几种影响其功能的蛋白质；我们已经 最近发现Rgt1p抑制物及其调节因子Grr1p是关键 葡萄糖诱导途径的组成部分。我们的长期目标是 了解葡萄糖是如何被感知的，以了解什么是信号以及它是如何 并确定它是如何被传递到基因调控的 改变基因表达的蛋白质：具体目标是： 。要了解葡萄糖抑制的机制： 我们将集中讨论葡萄糖抑制的两个中心问题：1)Mig1p如何 功能调节；2)Ga183p和Reg1p如何传递葡萄糖信号 对Mig1p功能的抑制物Snf1p蛋白激酶)？ 。要了解葡萄糖诱导机制： 我们打算1)确定葡萄糖如何抑制Rgt1p的功能 抑制者，2)了解Grr1p在这一过程中的作用，3)确定 几乎可以肯定的是，葡萄糖诱导途径的其他组成部分 是存在的。 。要了解葡萄糖信号的产生机制： 三个主要问题是：什么是葡萄糖传感器(S)，它是如何产生的 葡萄糖信号(S)，信号的性质是什么。致信地址 在这些问题上，我们建议1)测试葡萄糖转运蛋白的作用 葡萄糖传感器，2)分析出现的Snf3p葡萄糖转运体 作为低水平葡萄糖的传感器，以及3)测试葡萄糖类似物 它们产生葡萄糖诱导信号的能力。 。确定GAL4启动子的激活子，并了解其原因 软弱： 该启动子是酵母菌中最弱的启动子之一，似乎含有 新颖的功能元素。为了了解发起人实力的基础， 并确定调节转录因子表达的蛋白质 激活剂，我们建议1)分析新的类似TATA的UES/GAL4元件， 并确定通过它起作用的蛋白质，以及2)表征我们 已确定似乎通过UAS/GAL4元素起作用。

Glucose is the preferred carbon source for yeasts, as it is for most mammalian cells. Both types of organisms have evolved sophisticated regulatory mechanisms to optimize its utilization. In yeasts, glucose represses expression of many genes that are dispensables for cells growing on glucose (e.g., GAL genes), and induces expression of several genes necessary for efficient utilization (e.g., HXT genes, encoding glucose transporters); mammals have devised multiple mechanisms for maintaining glucose homeostasis. We believe that understanding glucose sensing and signalling mechanisms in the simple eukaroyte bakers' yeast (Saccharomyces cerevisiae) will inform the analysis the glucose signaling in larger eukaryotic cells. Both glucose repression and glucose induction of gene expression in yeast can be viewed as signal transduction pathways: extracellular glucose is sensed by receptors (possibly the glucose transporters), generating a signal that ultimately affects the function of gene regulatory proteins. Gene regulatory proteins for both pathways have been identified: the Mig1p repressor is a central component of the glucose repression pathway, and several proteins that affect its function have been identified; we have recently identified the Rgt1p repressor and its regulator, Grr1p, as a key components of the glucose induction pathway. Our long-term goals are to understand how glucose is sensed, to learn what the signal is and how it is generated, and to determine how it is transduced to the gene regulatory proteins to alter gene expression: The specific aims are: . To understand the mechanism of glucose repression: We will focus on two central issues of glucose repression: 1) how is Mig1p function regulated; 2) how do Ga183p and Reg1p transmit the glucose signal to the Snf1p protein kinase, an inhibitor of Mig1p function)? . To understand the glucose induction mechanism: We intend 1) determine how glucose inhibits function of the Rgt1p repressor, 2) learn the role of Grr1p in this process, and 3) identify other components of the glucose-induction pathway that almost certainly exist. . To understand the glucose signal-generation mechanism: Three main issues are: what is the glucose sensor(s), how does it generate the glucose signal(s), and what is the nature of the signal. To address these issues, we propose to 1) test the role of glucose transporters as glucose sensors, 2) analyze the Snf3p glucose transporter, which appears to be a sensor of low levels of glucose, and 3) test glucose analogs for their ability to generate a glucose induction signal. . To identify activators of the GAL4 promoter, and understand why it is so weak: This promoter, which is among the weakest in yeasts, appears to contain novel functional elements. To understand the basis of promoter strength, and identify proteins that regulate expression of transcriptional activators, we propose to 1) analyze the novel TATA-like UES/GAL4 element, and identify proteins that act through it, and 2) characterize proteins we have identified that appear to act through the UAS/GAL4 element.