Blumberg H, Hartshorne T A, Young E T
Department of Biochemistry, University of Washington, Seattle 98195.
Mol Cell Biol. 1988 May;8(5):1868-76. doi: 10.1128/mcb.8.5.1868-1876.1988.
Disruption of ADR1, a positive regulatory gene in the yeast Saccharomyces cerevisiae, abolished derepression of ADH2 but did not affect glucose repression of ADH2 or cell viability. The ADR1 mRNA was 5 kilobases long and had an unusually long leader containing 509 nucleotides. ADR1 mRNA levels were regulated by the carbon source in a strain-dependent fashion. beta-Galactosidase levels measured in strains carrying an ADR1-lacZ gene fusion paralleled ADR1 and ADR1-lacZ mRNA levels, indicating a lack of translational regulation of ADR1 mRNA. ADH2 was regulated by the carbon source to the same extent in all strains examined and showed complete dependence on ADR1 as well. The expression of ADR1 mRNA and an ADR1-beta-galactosidase fusion protein during glucose repression suggested that the activity of the ADR1 protein is regulated at the posttranslational level to properly regulate ADH2 expression. The ADR1-beta-galactosidase fusion protein was able to activate ADH2 expression during glucose repression but showed significantly higher levels of activation upon derepression. A similar result was obtained when ADR1 was present on a multicopy plasmid. These results suggest that low-level expression of ADR1 is required to maintain glucose repression of ADH2 and are consistent with the hypothesis that ADR1 is regulated at the posttranslational level.
ADR1是酿酒酵母中的一个正向调控基因，其功能的破坏消除了ADH2的去阻遏作用，但不影响ADH2的葡萄糖阻遏作用或细胞活力。ADR1 mRNA长5千碱基，有一个异常长的前导序列，包含509个核苷酸。ADR1 mRNA水平受碳源的菌株依赖性调控。在携带ADR1-lacZ基因融合的菌株中测得的β-半乳糖苷酶水平与ADR1和ADR1-lacZ mRNA水平平行，表明ADR1 mRNA缺乏翻译调控。在所有检测的菌株中，ADH2受碳源调控的程度相同，并且也完全依赖于ADR1。葡萄糖阻遏期间ADR1 mRNA和ADR1-β-半乳糖苷酶融合蛋白的表达表明，ADR1蛋白的活性在翻译后水平受到调控，以正确调节ADH2的表达。ADR1-β-半乳糖苷酶融合蛋白在葡萄糖阻遏期间能够激活ADH2的表达，但在去阻遏时显示出明显更高的激活水平。当ADR1存在于多拷贝质粒上时，也得到了类似的结果。这些结果表明，维持ADH2的葡萄糖阻遏需要ADR1的低水平表达，并且与ADR1在翻译后水平受到调控的假设一致。
