Cassart J P, Ostling J, Ronne H, Vandenhaute J
Unité de Recherches en Biologie Moléculaire, Facultés Norte-Darne de la Paix, Namur, Belgium.
Mol Gen Genet. 1997 Jun;255(1):9-18. doi: 10.1007/s004380050469.
The Mig1 repressor is a key effector in glucose repression in the yeast Saccharomyces cerevisiae. To gain further insights into structure-function relationships, we have now cloned the MIG1 homologue from the yeast Kluyveromyces marxianus. The amino acid sequence deduced from KmMIG1 differs significantly from ScMig1p outside the highly conserved zinc fingers. However, 12 discrete conserved motifs could be identified in a multiple alignment that also included the K. lactis Mig1p sequence. We further found that KmMig1p is fully functional when expressed in S. cerevisiae. First, it represses the SUC2 promoter almost as well as ScMig1p. This repression requires the Cyc8 and Tup1 proteins and is dependent on a C-terminal region comprising several conserved leucine-proline repeats. Second, KmMig1p is regulated by glucose in S. cerevisiae, and a KmMig1-VP16 hybrid activator is inhibited by the ScSnf1p kinase in the absence of glucose. This suggests that KmMig1p has retained the ability to interact with several S. cerevisiae proteins, and reinforces the notion that the conserved motifs are functionally important. Finally, we found that the physiological role of Mig1p also is conserved in K. marxianus, since KmMig1p represses INU1, the counterpart of SUC2 in this organism.
Mig1阻遏物是酿酒酵母葡萄糖阻遏中的关键效应因子。为了进一步深入了解结构与功能的关系，我们现已从马克斯克鲁维酵母中克隆出MIG1同源物。从KmMIG1推导的氨基酸序列在高度保守的锌指结构之外与ScMig1p有显著差异。然而，在多重比对中可以识别出12个离散的保守基序，该比对还包括乳酸克鲁维酵母的Mig1p序列。我们进一步发现，KmMig1p在酿酒酵母中表达时具有完全功能。首先，它对SUC2启动子的抑制作用几乎与ScMig1p一样好。这种抑制作用需要Cyc8和Tup1蛋白，并且依赖于包含几个保守亮氨酸-脯氨酸重复序列的C末端区域。其次，KmMig1p在酿酒酵母中受葡萄糖调节，并且在没有葡萄糖的情况下，KmMig1-VP16杂合激活剂会被ScSnf1p激酶抑制。这表明KmMig1p保留了与几种酿酒酵母蛋白相互作用的能力，并强化了保守基序在功能上很重要的观点。最后，我们发现Mig1p的生理作用在马克斯克鲁维酵母中也保守，因为KmMig1p抑制INU1，INU1是该生物体中SUC2的对应物。
