Research Interests
My lab investigates the molecular
mechanisms by which gene expression is regulated in the
budding yeast Saccharomyces
cerevisiae.
The
budding yeast S. cerevisiae prefers to ferment
glucose even when oxygen is abundant. This is called the
“Crabtree effect.” This specialized mode of glucose
metabolism yields only two ATPs per molecule of glucose
fermented, requiring yeast cells to pump large amounts
of glucose through glycolysis. They do this by enhancing
the rate-limiting step of glucose metabolism—glucose
transport—by increasing expression of the HXT
genes encoding glucose transporters. Glucose induction
of HXT expression is achieved via the
Snf3/Rgt2-Rgt1 signal transduction pathway, in which
glucose signal generated by the Snf3 and Rgt2 glucose
sensors ultimately alters function of the Rgt1
transcription factor. Yck1/2 phosphorylate Mth1 and
Std1, and the phosphorylated Mth1 and Std1 are recruited
by the SCFGrr1 for ubiquitination. The ensuing
ubiquitination of Mth1 and Std1 targets them to the 26S
proteasome for degradation. Degradation of Mth1 and Std1
robs Rgt1 of its ability to repress transcription by
promoting the dissociation of Rgt1 from the HXT
promoters, and thereby resulting in derepression of
HXT expression. These results support a view that
glucose directly binds their sensors, which triggers a
receptor-mediated signal transduction, as demonstrated
in hormone-induced signaling in mammals.
Publications
Representative Publications
Satish Pasula, David
JouandotII, and J. -H. Kim. 2007. Biochemical evidence
for glucose-independent induction of HXT expression in Saccharomyces cerevisiae.
FEBS Letters 581:3230-3234.
Kim, J. -H*,
and M. Johnston. 2006. Two glucose sensing pathways converge on Rgt1
to regulate expression of glucose transporter genes in S. cerevisiae.
J. Biol. Chem. 281:26144-26149. *Corresponding author.
Kim, J. -H,
V. Brachet, H. Moriya, and M. Johnston. 2006. Integration of transcriptional
and posttranslational regulation in a glucose signal transduction pathway
in Saccharomyces cerevisiae Eucaryotic Cell 5:167-173.
Johnston, M. and
J. -H. Kim. 2005. Glucose as a hormone: receptor-mediated glucose
sensing in the yeast S. cerevisiae. Biochem. Soc.Trans.
33:247-252. Review.
Kim, J. -H.
2004. Immobilized DNA-binding assay, an approach for
in vitro DNA-binding assay. Anal. Biochem.
334:401-402.
Kim, J. -H,
J. Polish, and M. Johnston. 2003. Specificity and regulation of DNA
binding by the yeast glucose transporter gene repressor Rgt1. Mol. Cell. Biol.
23:5208-5216.
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