Lutfiyya L L, Johnston M
Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Mol Cell Biol. 1996 Sep;16(9):4790-7. doi: 10.1128/MCB.16.9.4790.
Expression of the SUC2 gene in Saccharomyces cerevisiae, which encodes invertase, is repressed about 200-fold by high levels of glucose. Mig1p is a Cys2His2 zinc-finger-containing protein required for glucose repression of SUC2 and several other genes. However, SUC2 expression is still about 13-fold repressed by glucose in a mig1 mutant. We have identified a second repressor, Mig2p, containing zinc fingers very similar to those of Mig1p that is responsible for this remaining glucose repression of SUC2 expression. Overexpression of MIG2 represses SUC2 under nonrepressing conditions, and a LexA-Mig2p fusion represses transcription of a lexO-containing promoter in a glucose-dependent manner, supporting the idea that Mig2p is a glucose-activated repressor. We have shown that Mig2p binds to the Miglp-binding sites in the SUC2 promoter. Even though Mig1p and Mig2p bind to similar sites and share almost identical zinc fingers, they differ in their relative affinities for various Mig1p-binding sites. This could explain our observation that MIG2 appears to have little role in glucose repression of other promoters with MIG1-binding sites.
酿酒酵母中编码转化酶的SUC2基因的表达，会受到高浓度葡萄糖约200倍的抑制。Mig1p是一种含Cys2His2锌指的蛋白质，是SUC2和其他几个基因的葡萄糖抑制所必需的。然而，在mig1突变体中，SUC2的表达仍会受到葡萄糖约13倍的抑制。我们鉴定出了第二种阻遏物Mig2p，其含有的锌指与Mig1p的锌指非常相似，它负责对SUC2表达的剩余葡萄糖抑制作用。MIG2的过表达在非抑制条件下会抑制SUC2，并且LexA-Mig2p融合蛋白会以葡萄糖依赖的方式抑制含lexO启动子的转录，这支持了Mig2p是一种葡萄糖激活的阻遏物的观点。我们已经证明Mig2p会结合到SUC2启动子中的Miglp结合位点。尽管Mig1p和Mig2p结合到相似的位点并且共享几乎相同的锌指，但它们对各种Mig1p结合位点的相对亲和力不同。这可以解释我们的观察结果，即MIG2似乎在对其他具有Mig1p结合位点的启动子的葡萄糖抑制中作用不大。
