Frolova E, Johnston M, Majors J
Department of Biochemistry and Molecular Biophysics and Department of Genetics, Washington UniversitySchool of Medicine, 660 South Euclid, St Louis, MO 63110, USA.
Nucleic Acids Res. 1999 Mar 1;27(5):1350-8. doi: 10.1093/nar/27.5.1350.
Binding of the MIG1 repressor to the glucose-repressible GAL1 and GAL4 promoters was analyzed in vivo by cyclobutane dimer footprinting in two yeast strains that show different glucose repression responses. Mig1p binding to the two promoters in both strains was glucose-induced. In cells subject to rapid and stringent glucose repression (S288c), long-term Mig1p binding in glucose-grown cells was inhibited by the formation of a competing chromatin structure. Under conditions where glucose repression was only partially effective (gal80 - or low glucose), the chromatin structure did not form and long-term Mig1p binding was observed The same long-term binding of Mig1p was seen in cells of a different strain (W303A) that shows only partial glucose repression of the GAL1 promoter. We conclude from these experiments that Mig1p binding to glucose-repressed promoters is glucose-dependent but transient. We suggest that Mig1p functions at an early step in repression, but is not required to maintain the repressed state.
通过环丁烷二聚体足迹法，在两种表现出不同葡萄糖抑制反应的酵母菌株中，对MIG1阻遏物与葡萄糖可抑制的GAL1和GAL4启动子的结合进行了体内分析。在这两种菌株中，Mig1p与这两个启动子的结合均受葡萄糖诱导。在经历快速且严格的葡萄糖抑制的细胞（S288c）中，葡萄糖培养的细胞中Mig1p的长期结合受到竞争性染色质结构形成的抑制。在葡萄糖抑制仅部分有效的条件下（gal80 - 或低葡萄糖），染色质结构未形成，且观察到Mig1p的长期结合。在另一种菌株（W303A）的细胞中也观察到了Mig1p的相同长期结合，该菌株仅对GAL1启动子表现出部分葡萄糖抑制。我们从这些实验得出结论，Mig1p与葡萄糖抑制的启动子的结合是葡萄糖依赖性的，但具有短暂性。我们认为Mig1p在抑制的早期阶段起作用，但维持抑制状态并不需要它。
