Analysis of the GAL3 signal transduction pathway activating GAL4 protein-dependent transcription in Saccharomyces cerevisiae.
Analysis of the GAL3 signal transduction pathway activating GAL4 protein-dependent transcription in Saccharomyces cerevisiae.
复制标题
分析酿酒酵母中 GAL3 信号转导通路激活 GAL4 蛋白依赖性转录。
DOI：
10.1093/genetics/125.2.281
复制
发表时间：
1990
期刊：
影响因子：
3.3
通讯作者：
Hopper,JE
中科院分区：
文献类型：
--
作者：
Bhat,PJ;Oh,D;Hopper,JE
酿酒酵母GAL/MEL调节子基因通常在半乳糖添加的几分钟内被诱导，但gal 3突变体表现出3-5天的诱导滞后。我们已经发现，gal 3赋予的这种长期适应（LTA）表型由GAL 1基因的多个拷贝补充。基于这一结果以及GAL 3和GAL 1蛋白序列之间惊人的相似性，我们试图检测可能与GAL 3蛋白相关的半乳糖激酶活性。通过体内和体外试验，GAL 3基因产物似乎不催化半乳糖激酶样反应。在补充实验中，大肠杆菌半乳糖激酶在酵母中表达，以补充gal 1，但不是gal 3突变。因此，GAL 1提供的互补活性不太可能是由于半乳糖激酶活性，而是由于独特的GAL 3样活性。总体而言，结果表明GAL 1编码双功能蛋白。在相关实验中，我们测试了缺乏其他基因功能的gal 3细胞中LTA诱导途径的功能。人们已经知道gal 3gal 1，gal 3gal 7，gal 3gal 10和gal 3 rho--不能诱导。我们构建了与gal 15或pgi 1突变组合的gal 3突变的同基因单倍体菌株：gal 15和pgi 1块与gal 1，gal 7和gal 10块相比，对半乳糖途径不是特异性的。gal 3gal 5和gal 3 pgi 1双突变体是不可诱导的，而gal 5和pgi 1单突变体都是可诱导的。我们的结论是，除了GAL 1的GAL 3样活性，功能超出半乳糖特异性GAL 1，GAL 7和GAL 10酶所需的LTA诱导途径。
The Saccharomyces cerevisiae GAL/MEL regulon genes are normally induced within minutes of galactose addition, but gal3 mutants exhibit a 3-5-day induction lag. We have discovered that this long-term adaptation (LTA) phenotype conferred by gal3 is complemented by multiple copies of the GAL1 gene. Based on this result and the striking similarity between the GAL3 and GAL1 protein sequences we attempted to detect galactokinase activity that might be associated with the GAL3 protein. By both in vivo and in vitro tests the GAL3 gene product does not appear to catalyze a galactokinase-like reaction. In complementary experiments, Escherichia coli galactokinase expressed in yeast was shown to complement the gal1 but not the gal3 mutation. Thus, the complementation activity provided by GAL1 is not likely due to galactokinase activity, but rather due to a distinct GAL3-like activity. Overall, the results indicate that GAL1 encodes a bifunctional protein. In related experiments we tested for function of the LTA induction pathway in gal3 cells deficient for other gene functions. It has been known for some time that gal3gal1, gal3gal7, gal3gal10, and gal3 rho--are incapable of induction. We constructed isogenic haploid strains bearing the gal3 mutation in combination with either gal15 or pgi1 mutations: the gal15 and pgi1 blocks are not specific for the galactose pathway in contrast to the gal1, gal7 and gal10 blocks. The gal3gal5 and gal3pgi1 double mutants were not inducible, whereas both the gal5 and pgi1 single mutants were inducible. We conclude that, in addition to the GAL3-like activity of GAL1, functions beyond the galactose-specific GAL1, GAL7 and GAL10 enzymes are required for the LTA induction pathway.