Catabolite
degradation of fructose-1,6-bisphosphatase in the yeast Saccharomyces
cerevisiae
: a genome-wide screen identifies eight novel GID-genes and indicates
the existence of two degradation pathways.
Jochen Regelmann (1), Thomas Schüle (1), Frank S. Josupeit (1), Jaroslav Horak
(2), Matthias Rose (3), Karl-Dieter Entian (3), Michael Thumm (1), Dieter H.
Wolf (1)
(1) Institute of Biochemistry, University of Stuttgart, Pfaffenwaldring 55,
Stuttgart, 70569, Germany (jochen.regelmann@brs-concepts.de); (2) Czech Academy
of Sciences, Institute of Physiology, Videnska 1083, 14220 Prague, Czech
Republic; (3) Institute of Microbiology, Johann Wolfgang Goethe-University
Frankfurt, Marie-Curie-Straße 9, 60439 Frankfurt, Germany
Metabolic adaptation of Saccharomyces cerevisiae cells from a non-fermentable carbon source to glucose induces selective, rapid breakdown of the gluconeogenetic key enzyme fructose-1,6-bisphosphatase (FBPase), a process called catabolite degradation. We identified eight novel GID-genes, required for proteasome dependent catabolite degradation of FBPase. The site of catabolite degradation has been controversial up till now. Two FBPase degradation pathways have been described, one dependent on the cytosolic ubiquitin-proteasome machinery, the other dependent on vacuolar proteolysis. Interestingly, three of the novel Gid-proteins involved in ubiquitin-proteasome dependent degradation have also been reported by others to affect the vacuolar degradation pathway. As shown here, additional genes suggested to be essential for vacuolar degradation, are unnecessary for proteasome dependent degradation. These data raise the question as to whether two FBPase degradation pathways exist, which share components. Detailed characterization of Gid2p demonstrates, that it is part of a soluble, cytosolic protein complex of at least 600 kDa. Gid2p is necessary for FBPase-ubiquitination. Our studies have not revealed any involvement of vesicular intermediates in proteasome dependent FBPase degradation. The influence of Ubp14p, a de-ubiquitinating enzyme, on proteasome dependent catabolite degradation was further uncovered.