NUTRITIONAL AND HORMONAL REGULATION OF HEPATIC GENES

哺乳动物生物体调节其遗传信息的表达 对营养和代谢信号的反应;然而， 目前已知的分子机制涉及这些 流程.这项工作的长期目标是了解一个系统 代谢调节的关键这个系统涉及酶的诱导 响应于增加的碳水化合物而催化肝脏中的脂肪生成 新陈代谢.我们集中在两个基因-L型丙酮酸激酶 (PK)和S14基因-这些基因被转录激活， 肝细胞中的葡萄糖代谢。过去的工作已确定具体的 在这些基因的5 '侧翼区发现的调节区， 是控制的必要和充分条件。这些地区有一个共同点， 包括两个元件的装置：碳水化合物响应元件 （ChoRE）本身能够对葡萄糖增加做出反应 代谢和一个辅助因子的网站，提高了响应。的 ChoRE包含两个E盒基序（CACGTG）的独特排列， 间隔5个碱基对。我们假设这个元素作为 碳水化合物响应因子或复合物的结合位点。 了解这种转录因子的性质是第一个 这项工作的目标。这将通过以下方式解决：（1）确定 与序列CACGTG结合的因子USF是否是 碳水化合物响应复合物的组分;（2）分离和 从大鼠肝脏克隆与ChoRE结合的因子;和（3） 鉴定所述碳水化合物响应性复合物的其它组分 使用蛋白质相互作用筛选参与基因调控。与此 信息，我们将继续研究，探讨 在肝细胞中进行糖酵解升高的因子活化。 特别是，我们将探讨磷酸化在这一过程中的作用。 过程最后，我们将描述一个新的配件的性质 与PK和S14基因结合的因子，并确定这是否 因子参与接收来自其他生理信号 这些基因的调控者。这些研究应该有助于破译 肝细胞可以感知糖酵解增加的信号传导过程 并通过改变其转录程序做出反应， 在高等真核生物中，营养素对转录的调节作用。

Mammalian organisms regulate the expression of their genetic information in response to nutritional and metabolic signals; however, little is currently known regarding the molecular mechanisms involved in these processes. The long range goal of this work is to understand one system of metabolic regulation. This system involves the induction of enzymes catalyzing lipogenesis in the liver in response to increased carbohydrate metabolism. We have focused on two genes - the L-type pyruvate kinase (PK) and S14 genes - that are transcriptionally activated by increased glucose metabolism in the hepatocyte. Past work has defined specific regulatory regions found in the 5'-flanking region of these genes that are necessary and sufficient for control. These regions share a common arrangement including two elements: a carbohydrate response element (ChoRE) that by itself is capable of responding to increased glucose metabolism and an accessory factor site that enhances the response. The ChoRE contains a unique arrangement of two E box motifs (CACGTG) that are spaced by 5 base pairs. We hypothesize that this element serves as the binding site for a carbohydrate-responsive factor or complex. Understanding the nature of this transcriptional factor is the first objective of this work. This will be addressed by: (1) determining whether the factor USF, which binds to the sequence CACGTG, is a component of the carbohydrate-responsive complex; (2) isolating and cloning the factor binding to the ChoRE from rat liver; and (3) identifying other components of the carbohydrate-responsive complex involved in gene regulation using a protein interaction screen. With this information, we will pursue studies to explore the mechanism of activation of the factor in hepatocytes undergoing elevated glycolysis. In particular, we will explore the role of phosphorylation in this process. Finally, we will characterize the nature of a novel accessory factor that binds to both the PK and S14 genes and determine whether this factor is involved in receiving signals from other physiological regulators of these genes. These studies should help in deciphering the signaling process by which the hepatocyte can sense increased glycolysis and respond by changing its transcriptional program and serve as a model for transcriptional regulation by nutrients in higher eucaryotes.