Yeast Genetics and Molecular Biology 2000
University of Washington
Seattle, Washington USA
July 2000

Name: Wolf, Dieter H.
Mailing Address: Institut fuer Biochemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, , Germany
Email Address: dieter.wolf@po.uni-stuttgart.de
Phone & FAX numbers: ++49-711-6854390 & ++49-711-6854392

#020

Ubc8p functions in catabolite degradation of fructose-1,6-bisphosphatase in yeast.
Dieter H. Wolf (1), Matthias Rose (2), Karl-Dieter Entian (2), Michael Thumm (1), Thomas Schuele (1)
(1) Institut fuer Biochemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany; (2) Institut fuer Mikrobiologie, Johann Wolfgang Goethe-Universitaet Frankfurt, Marie-Curie-Strasse 9, 60349 Frankfurt, Germany

The key gluconeogenetic enzyme fructose-1,6-bisphosphatase (FBPase) is synthesized when cells of the yeast Saccharomyces cerevisiae are grown on a non-fermentable carbon source. After shifting the cells to glucose containing medium, in a process called catabolite degradation, FBPase is selectively and rapidly broken down. We had isolated gid-mutants which are defective in this glucose-induced degradation process (Haemmerle et al., 1998). When complementing the defect in catabolite degradation of FBPase in gid3-1 mutant cells with a yeast genomic library, we identified the GID3 gene and found it to be identical with UBC8 encoding the ubiquitin-conjugating enzyme Ubc8p. The in vivo function of Ubc8p (Gid3p) had been remained a mystery so far. Here we demonstrate the involvement of Ubc8p in the glucose-induced ubiquitination of FBPase being a prerequisite for catabolite degradation of the enzyme via the proteasome. Like FBPase, Ubc8p is found in the cytoplasmic fraction of the cell. We demonstrate cytoplasmic degradation of FBPase.

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