ISOLATION OF THE YEAST REGULATORY GENE GAL4 AND ANALYSIS OF ITS DOSAGE EFFECTS ON THE GALACTOSE MELIBIOSE REGULON
ISOLATION OF THE YEAST REGULATORY GENE GAL4 AND ANALYSIS OF ITS DOSAGE EFFECTS ON THE GALACTOSE MELIBIOSE REGULON
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DOI：
10.1073/pnas.79.22.6971
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发表时间：
1982-01-01
期刊：
影响因子：
--
通讯作者：
HOPPER, JE
中科院分区：
文献类型：
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作者：
JOHNSTON, SA;HOPPER, JE
GAL4 是一个经典定义的正调控基因，控制酵母中半乳糖/蜜二糖利用的 5 个可诱导结构基因。 GAL4 基因产物的正调节功能又受另一个基因产物（负调节因子 GAL80）的控制。利用多拷贝嵌合载体YEp24通过同源互补克隆了含有GAL4的3.1-kilobase片段，并证明酵母中多拷贝的GAL4对结构基因的表达具有显着的剂量效应。用携带 GAL4 的质粒转化的酵母成为半乳糖/蜜二糖基因表达的组成型，即使在正常抑制（葡萄糖）培养基中也是如此。 GAL4 质粒的多个拷贝还可以增加诱导（半乳糖）培养基中结构基因的表达，并且可以部分克服显性超阻遏突变体 GAL80 的影响。使用 GAL4 中的内部缺失，证明这些剂量效应是由于 GAL4 正调节产物的过量产生，而不是侧翼序列滴定负调节产物的影响。这些结果表明正调节蛋白和负调节蛋白之间的竞争性相互作用在控制该系统中的重要性。 GAL4质粒的剂量效应还与不同的GAL4和GAL80等位基因结合使用以创建新的表型。这些表型被解释为表明葡萄糖的抑制作用至少部分是由负调节基因 GAL80 的产物介导的，并且 GAL80 蛋白可能与结构基因的控制区域具有特定的相互作用。
GAL4 is a classically defined positive regulatory gene controlling the 5 inducible structural genes of galactose/melibiose utilization in yeast. The positive regulatory function of the GAL4 gene product in turn is controlled by the product of another gene, the negative regulator GAL80. A 3.1-kilobase fragment containing GAL4 was cloned by homologus complementation using the multicopy chimeric vector YEp24 and it was demonstrated that multiple copies of GAL4 in yeast have pronounced dosage effects on the expression of the structural genes. Yeast transformed with GAL4-bearing plasmid become constitutive for expression of the galactose/melibiose genes, even in normally repressing (glucose) medium. Multiple copies of the GAL4 plasmid also increase expression of the structural genes in inducing (galactose) medium and can partially overcome the effects of a dominant super-repressor mutant, GAL80s. Using an internal deletion in GAL4, it was demonstrated that these dosage effects are due to overproduction of GAL4 positive regulatory product rather than an effect of the flanking sequences titrating out a negative regulator. These results point to the importance of competitive interplay between the positive and negative regulatory proteins in the control of this system. The dosage effect of GAL4 plasmid was also used in combination with different GAL4 and GAL80 alleles to create new phenotypes. These phenotypes are interpreted as indicating that the repressing effects of glucose, at least in part, are mediated by the product of the negative regulatory gene, GAL80, and the GAL80 protein may have specific interactions with the control regions of the structural genes.