Rahner A, Schöler A, Martens E, Gollwitzer B, Schüller H J
Institut für Mikrobiologie, Biochemie und Genetik, Lehrstuhl Biochemie, Universität Erlangen/Nürnberg, Erlangen, Germany.
Nucleic Acids Res. 1996 Jun 15;24(12):2331-7. doi: 10.1093/nar/24.12.2331.
The CSRE (carbon source-responsive element) is a sequence motif responsible for the transcriptional activation of gluconeogenic structural genes in Saccharomyces cerevisiae. We have isolated a regulatory gene, DIL1 (derepression of isocitrate lyase, = CAT8), which is specifically required for derepression of CSRE-dependent genes. Expression of CAT8 is carbon source regulated and requires a functional Cat1p (Snf1p) protein kinase. The derepression defect of CAT8 in a cat1 mutant could be suppressed by a mutant Mig1p repressor protein. Derepression of CAT8 also requires a functional HAP2 gene, suggesting a regulatory connection between respiratory and gluconeogenic genes. Carbon source-dependent protein-CSRE complexes detected in a gel retardation analysis with wild-type extracts were absent in cat8 mutant extracts. However, similar experiments with an epitope-tagged CAT8 gene product in the presence of tag-specific antibodies gave evidence against a direct binding of Cat8p to the CSRE. A constitutively expressed GAL4-CAT8 fusion gene revealed a carbon source-dependent transcriptional activation of a UAS(GAL)-containing reporter gene. Activation mediated by Cat8p was no longer detectable in a cat1 mutant. Thus, biosynthetic control of CAT8 as well as transcriptional activation by Cat8p requires a functional Cat1p protein kinase. A model proposing CAT8 as a specific activator of a transcription factor(s) binding to the CSRE is discussed.
碳源响应元件（CSRE）是一种序列基序，负责酿酒酵母中糖异生结构基因的转录激活。我们分离出了一个调控基因DIL1（异柠檬酸裂解酶去阻遏，=CAT8），它是CSRE依赖性基因去阻遏所特需的。CAT8的表达受碳源调控，并且需要功能性的Cat1p（Snf1p）蛋白激酶。cat1突变体中CAT8的去阻遏缺陷可被突变型Mig1p阻遏蛋白抑制。CAT8的去阻遏还需要功能性的HAP2基因，这表明呼吸和糖异生基因之间存在调控联系。在使用野生型提取物进行的凝胶阻滞分析中检测到的碳源依赖性蛋白-CSRE复合物在cat8突变体提取物中不存在。然而，在存在标签特异性抗体的情况下，用表位标签化的CAT8基因产物进行的类似实验提供了证据，反对Cat8p与CSRE直接结合。一个组成型表达的GAL4-CAT8融合基因显示了含UAS（GAL）的报告基因的碳源依赖性转录激活。在cat1突变体中不再能检测到由Cat8p介导的激活。因此，CAT8的生物合成控制以及Cat8p的转录激活都需要功能性的Cat1p蛋白激酶。本文讨论了一个将CAT8作为与CSRE结合的转录因子的特异性激活剂的模型。
