Abstract
Expression of the HXT1 gene, which encodes a low affinity glucose transporter in Saccharomyces cerevisiae, is regulated positively in response to glucose by the general glucose induction pathway, involving the Snf3/Rgt2 membrane glucose sensors, the SCF-Grr1 ubiquitination complex and the Rgt1 transcription factor. In this study we show that, in addition to the glucose signaling pathway, regulation of HXT1 expression also requires the HOG pathway. Deletion of components in the glucose signaling pathway or in the HOG pathway results in impaired HXT1 expression. Genetic analyses showed that, whereas the glucose signaling pathway regulates HXT1 through modulation of the Rgt1 transcription factor, the HOG pathway modulates HXT1 through regulation of the Sko1-Tup1-Ssn6 complex. Coordinated regulation of the two signaling pathways is required for expression of HXT1 by glucose and in response to osmostress.
Highlights
The Cys6-Zinc cluster protein family, which acts as a transcriptional repressor in the absence of glucose [3, 7]
The HOG Pathway Regulates HXT1 Gene Expression by Glucose and Osmostress—Expression of the HXT1 low affinity glucose transporter is regulated by glucose availability, being inhibited when glucose levels are scarce and activated in the presence of the sugar
To rule out the possibility that the absence of Hog1 kinase could stimulate the activity of the Snf1 kinase and inhibit HXT1 expression, we studied the activity of Snf1 protein kinase in a hog1⌬ mutant by analyzing the regulation of the expression of SUC2 and found that it was similar to wild type (Table II)
Summary
MATa his leu trp ura MAT␣ hog1⌬::TRP1 derivative of TM141 MATa snf1⌬::KanMX hog1⌬::TRP1 of TM141 MATa pbs2⌬::LEU2 derivative of TM141 MATa ste11⌬::HIS3 ssk2⌬::LEU2 ssk22⌬::LEU2 his leu ura MATa sho1⌬::TRP1 ste11⌬::HIS3 derivative of TM141 MAT␣ ssk2⌬::LEU2 ssk22⌬::LEU2 leu trp ura MATa ade his leu trp ura can MATa snf1⌬::KanMX derivative of W303 MATa msn2⌬::HIS3 msn4⌬::TRP1 derivative of W303 MATa rgt1⌬::KanMX derivative of W303 MATa rgt1⌬::KanMX hog1⌬::TRP1 derivative of W303 MATa tup1⌬::KanMX derivative of W303 MATa tup1⌬::KanMX hog1⌬::TRP1 derivative of W303 MATa sko1⌬::KanMX derivative of W303 MATa sko1⌬::KanMX hog1⌬::TRP1 derivative of W303 MATa sko1⌬::KanMX rgt1⌬::URA3 derivative of W303 MATa his leu trp ura MATa snf3⌬::hisG rgt2⌬::HIS3 derivative of MSY401 MATa std1⌬::HIS3 mth1⌬2 derivative of MSY401 MATa std1⌬::HIS3 mth1⌬2 hog1⌬::TRP1 derivative of MSY401 MAT␣ his leu trp ura MAT␣ grr (cat80–24) derivative of ENY.WA-1A MAT␣ ura leu his rgt1::KAN YIp368R-HXT1 (LEU2) MATa ura leu trp his rgt1::KAN YIp358R HXT1 (URA3). Reference [16] [16] This study [42] [42] [42] [42] [43] This study [44] This study This study [18] This study [18] This study This study [9] [9] [9] This study [45] [45] This study This study (provided glucose was present) requires the coordinated activity of two independent signaling pathways that converge at the promoter level of HXT1
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