REGULATION OF ISOLEUCINE/VALINE BIOSYNTHESIS

我们感兴趣的是细胞协调 表达其生长所需的各种基因。人类的基因 异亮氨酸/缬氨酸生物合成被分成四个独立的 转录单位。独立监管，但对 相似的信号(即细胞内亮氨酸、异亮氨酸的浓度 和Valine)。对于最佳细胞生长来说，重要的是 这些基因的产物被协调以提供所需的平衡 这些氨基酸。四个基因结合在一起形成了ilvGEDA操纵子， 其中包含多个监管站点，从而实现所需的 基因产物的平衡。监管的主要地点是 ILVG近端的促进器衰减器。操作员内的辅助站点 包括：两个内部发起人和一个内部终止地点。 目前，我们对这些元素是如何形成的只有一个初步的了解 结合起来控制这些基因编码的酶的水平。在……里面 为了研究监管部门之间的相互关系 IlvGEDA操纵子，我们建议研究每个调控元件的作用 通过使用重组DNA技术在体外构建的基因融合。 在每一次融合中，一个ilv调节元件将被插入到一个质粒中。 使得质粒基因表达依赖于插入的ILV DNA然后，这些质粒会受到体外诱变， 改变的质粒检测改变的基因表达。后续分析 通过体外转录和DNA序列测定将有助于 我们确定了每个监管要素的性质和特征。 因为一组基因表达的协调是必不可少的 对于细胞功能，我们认为重要的是确定 实现这种协调的机制。人类的基因 异亮氨酸/缬氨酸的生物合成形成了这样一组。因为这些生物的DNA 基因已经被分离和鉴定，它们很容易被访问 详细分析了他们的监管。

We are interested in the mechanism by which a cell coordinates the expression of the various genes required for its growth. The genes for isoleucine/valine biosynthesis are separated into four separate transcriptional units. That are regulated independently but respond to similar signals (i.e., intracellular concentrations of leucine, isoleucine and valine). It is important for optimal cell growth that the level of the products of these genes be coordinated to supply the required balance of these amino acids. Four of the genes combine to form the ilvGEDA operon, which contains multiple regulatory sites so as to achieve the requisite balance of gene products. The primary site of regulation is the promoterattenuator proximal to ilvG. Secondary sites within the operon include: two internal promoters and an internal termination site. Presently, we have only a rudimentary understanding of how these elements combine to control the level of the enzymes encoded by these genes. In order to study the interrelationship of the regulatory components of the ilvGEDA operon, we propose to examine the role of each regulatory element by using gene fusions constructed in vitro by recombinant DNA techniques. In each fusion an ilv regulatory element will be inserted into a plasmid such that expression of a plasmid gene is dependent on the inserted ilv DNA. These plasmids will then be subjected to in vitro mutagenesis and the altered plasmids examined for altered gene expression. Subsequent analysis by in vitro transcription and DNA sequence determination will facilitate our establishing the nature and character of each regulatory element. Because the coordination of the expression of sets of genes is essential for cellular function, we believe it is important to determine the mechanisms by which this coordination is achieved. The genes for isoleucine/valine biosynthesis form such a set. Because the DNA of these genes has been isolated and characterized, they are readily accessible for detailed analysis of their regulation.