Jeong-Ho Kim, Ph.D.

Ph.D., 1997, University of Wisconsin-Madison
Postdoc, 1998-2005, Washington University-St. Louis

Dr. Kim's primary research interest is in glucose sensing and signaling in 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.