Kuger P, Gödecke A, Breunig K D
Institute of Microbiology, Heinrich-Heine-Universität, Düsseldorf, FRG.
Nucleic Acids Res. 1990 Feb 25;18(4):745-51. doi: 10.1093/nar/18.4.745.
The transcriptional activator LAC9, a GAL4 homolog of Kluyveromyces lactis which mediates lactose and galactose-dependent activation of genes involved in the utilization of these sugars can also confer glucose repression to those genes. Here we report on the isolation and characterization of LAC9-2, an allele which encodes a glucose-sensitive activator in contrast to the one previously cloned. A single amino acid exchange of leu-104 to tryptophan is responsible for the glucose-insensitive phenotype. The mutation is located within the Zn-finger-like DNA binding domain which is highly conserved between LAC9 and GAL4. Glucose repression is also eliminated by duplication of the LAC9-2 allele. The data indicate that LAC9 is a limiting factor for beta-galactosidase gene expression under all growth conditions and that glucose reduces the activity of the activator.
转录激活因子LAC9是乳酸克鲁维酵母的一种GAL4同源物，它介导乳糖和半乳糖依赖的参与这些糖利用的基因的激活，同时也能赋予这些基因葡萄糖阻遏作用。在此，我们报道了LAC9 - 2的分离和特性，该等位基因编码一种与先前克隆的不同的葡萄糖敏感激活因子。亮氨酸104到色氨酸的单个氨基酸交换导致了葡萄糖不敏感表型。该突变位于LAC9和GAL4之间高度保守的锌指样DNA结合结构域内。LAC9 - 2等位基因的重复也消除了葡萄糖阻遏作用。数据表明，LAC9在所有生长条件下都是β - 半乳糖苷酶基因表达的限制因素，并且葡萄糖会降低激活因子的活性。
