Regulated degradation of the transcription factor Gcn4.
We report that Gcn4, a yeast transcriptional activator of the bZIP family involved in the regulation of the biosynthesis of amino acids and purines, is rapidly turned over. This degradation is inhibited under conditions of starvation for amino acids. Degradation is also inhibited by single amino acid alterations in a region adjacent to the Gcn4 activation domain. Furthermore, we show that degradation of Gcn4 proceeds through the ubiquitin pathway, a major proteolytic system for cytoplasmic proteins, and is dependent on two specific ubiquitin conjugating enzymes, Cdc34 (Ubc3) and Rad6 (Ubc2). As a first step towards reconstituting the Gcn4 degradation pathway in vitro, we show that purified Cdc34 and Rad6 proteins are able to direct the specific ubiquitination of Gcn4.
Kornitzer
D
D
Whitehead Institute, Nine Cambridge Center, MA 02142.
Raboy
B
B
Kulka
R G
RG
Fink
G R
GR
D000596:Amino Acids / Q000172:deficiency; D064173:Anaphase-Promoting Complex-Cyclosome; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism; D008954:Models, Biological; D017354:Point Mutation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism*
D000596:Amino Acids; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014452:Ubiquitins; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; D008025:Ligases