STRUCTURE AND ORGANIZATION OF YEAST MAL LOCI

遗传分析表明，在中国汉族人群中存在一个由5个非连锁的MAL基因座组成的家系。 酵母，其中任何一种都足以将麦芽糖转化为葡萄糖。 的 从我们以前的研究中获得的证据表明，MAL1和MAL6 是由至少3个基因组成的复杂基因座：麦芽糖通透酶基因， 麦芽糖酶基因和其产物控制该坐标的调节基因 麦芽糖通透酶和麦芽糖酶诱导。 Southern blot 杂交证明所有5个MAL基因座共享序列同源性。 该提案的主旨是更详细地调查 组织，相关性和端粒位置的性质， 使用重组DNA和遗传技术的MAL基因座。 我们现在克隆了 MAL6、MAL2、MAL4和MAL1的两个无功能等位基因。 Cosmid和Lambda 载体将用于克隆剩余的MAL基因座。 克隆和亚克隆 MAL基因座和相邻序列将经受限制性酶， 交叉杂交和异源双链体分析以研究它们的相关性。 这种分析还将确定专题组的职能组织 在不同的MAL基因座内的基因。 在相关研究中，DNA测序 MAL6基因座的研究进展顺利。 MAL1的普遍存在 基因座（或其等位基因之一）在许多实验室菌株表明，它 可能是其他MAL基因座的祖先。 实验将被指导 研究MAL基因座是如何分散的。 的机理 编码转化酶的SUC基因座的分散可以类似于编码转化酶的SUC基因座的分散。 MAL基因座; SUC1似乎已被转座到mal1附近。 的 MAL1/SUC1的关系，两个非常紧密连锁的标记，将是 研究了 将在体内和体外继续进行密集的遗传分析 产生了Mal突变体，主要是在MAL1（和MAL6）基因座上， 使这两个基因座的遗传图谱饱和。 基因、生理和 对这些突变体的物理分析应该特别允许我们：（1） 建立结构-功能关系;（2）提供适当的 （3）帮助确定补充研究的作用; 调节蛋白及其作用位点;（4）检测遗传交换 （5）帮助定义MALp和MALg的功能， Naumov是MAL基因座的组成部分。 基因和物理分析 应该使我们能够确定功能和物理同源性的程度 5个MAL基因座间均存在着多态性。

Genetic analysis has shown that there is a family of 5 unlinked MAL loci in yeast, any one of which is sufficient to convert maltose to glucose. The evidence obtained from our previous studies demonstrates that MAL1 and MAL6 are complex loci consisting of at least 3 genes: a maltose permease gene, a maltase gene and a regulatory gene whose product controls the coordinate induction of maltose permease and maltase. In addition, Southern blot hybridizations demonstrate that all 5 MAL loci share sequence homology. The main thrust of the proposal is to investigate in greater detail the organization, relatedness and the nature of the telomeric locations of the MAL loci using recombinant DNA and genetic techniques. We have now cloned MAL6, MAL2, MAL4 and two non-functional alleles of MAL1. Cosmid and Lambda vectors will be used to clone the remaining MAL loci. Cloned and subcloned MAL loci and adjacent sequences will be subjected to restriction enzyme, cross-hybridization and heteroduplex analyses to study their relatedness. Such analyses will also define the functional organization of the cluster of genes within the different MAL loci. In related studies, DNA sequencing of the MAL6 locus is well underway. The ubiquitous presence of the MAL1 locus (or one of its alleles) in many laboratory strains indicates that it may be the progenitor of the other MAL loci. Experiments will be directed to investigate how the MAL loci may have been dispersed. The mechanism of dispersion of the SUC loci encoding invertase may be similar to that of the MAL loci; SUC1 appears to have been transposed adjacent to mal1. The relationship of MAL1/SUC1, two very closely linked markers, will be investigated. An intensive genetic analysis will be continued on in vivo and in vitro generated Mal mutants, primarily at the MAL1 (and MAL6) loci in order to saturate the genetic map of these two loci. The genetic, physiological and physical analysis of these mutants should specifically allow us to: (1) Establish structure-function relationships; (2) provide appropriate recipients in complementation studies; (3) help to define the role of the regulatory protein and its site(s) of action; (4) examine genetic exchange between loci; and (5) help define the MALp and MALg functions designated by Naumov to be components of MAL loci. The genetic and physical analyses should allow us to determine the degree of functional and physical homology existing among all 5 MAL loci.