Glucose, fructose and mannose are the preferred carbon/energy sources for the yeast Saccharomyces cerevisiae. Absence of preferred energy sources activates glucose derepression, which is regulated by the kinase Snf1. Snf1 phosphorylates the transcriptional repressor Mig1, which results in its exit from the nucleus and subsequent derepression of genes. In contrast, Snf1 is inactive when preferred carbon sources are available, which leads to dephosphorylation of Mig1 and its translocation to the nucleus where Mig1 acts as a transcription repressor. Here we revisit the role of the three hexose kinases, Hxk1, Hxk2 and Glk1, in glucose de/repression. We demonstrate that all three sugar kinases initially affect Mig1 nuclear localization upon addition of glucose, fructose and mannose. This initial import of Mig1 into the nucleus was temporary; for continuous nucleocytoplasmic shuttling of Mig1, Hxk2 is required in the presence of glucose and mannose and in the presence of fructose Hxk2 or Hxk1 is required. Our data suggest that Mig1 import following exposure to preferred energy sources is controlled via two different pathways, where (1) the initial import is regulated by signals derived from metabolism and (2) continuous shuttling is regulated by the Hxk2 and Hxk1 proteins. Mig1 nucleocytoplasmic shuttling appears to be important for the maintenance of the repressed state in which Hxk1/2 seems to play an essential role.

葡萄糖，果糖和甘露糖是酿酒酵母的首选碳/能量来源。缺少首选的能源会激活葡萄糖减阻，这由激酶Snf1调节。Snf1使转录阻遏物Mig1磷酸化，导致其从细胞核中退出并随后抑制基因。相反，当可以使用首选的碳源时，Snf1是无活性的，这会导致Mig1的去磷酸化以及其转位到Mig1充当转录抑制子的核中。在这里，我们重新审视三种己糖激酶Hxk1，Hxk2和Glk1在葡萄糖去抑制中的作用。我们证明，添加葡萄糖，果糖和甘露糖后，所有三个糖激酶最初都会影响Mig1核定位。最初将Mig1导入细胞核是暂时的。用于Mig1的连续核质穿梭，在葡萄糖和甘露糖存在下以及在果糖存在下需要Hxk2。Hxk2或Hxk1是必需的。我们的数据表明，暴露于首选能源后，Mig1的导入通过两种不同的途径进行控制，其中（1）初始导入受代谢信号调控，（2）连续穿梭受Hxk2和Hxk1蛋白调控。Mig1核质穿梭似乎对于维持Hxk1 / 2似乎起重要作用的抑制状态很重要。