Proteolysis-independent regulation of the transcription factor Met4 by a single Lys 48-linked ubiquitin chain.
The ubiquitin ligase SCF(Met30) is required for cell cycle progression in budding yeast. The critical function of SCF(Met30) is inactivation of the transcriptional activator Met4. Here we show that a single ubiquitin chain is attached to Met4 through lysine at position 163. Inhibition of Met4 ubiquitination by mutating lysine to arginine at this position constitutively activates, but does not stabilize, Met4. This supports a proteolysis-independent role of Cdc34-SCF(Met30)-catalysed Met4 ubiquitination. Surprisingly, the ubiquitin chain attached to Met4 is linked through Lys 48 in ubiquitin, a ubiquitin chain structure that is usually required for substrate targeting to the 26S proteasome. These results suggest that Lys 48-linked ubiquitin chains can have a regulatory role independent of proteolysis.
Flick
Karin
K
Department of Biological Chemistry, University of California Irvine, Irvine, CA 92697, USA.
Ouni
Ikram
I
Wohlschlegel
James A
JA
Capati
Chrissy
C
McDonald
W Hayes
WH
Yates
John R
JR
Kaiser
Peter
P
D050976:Basic-Leucine Zipper Transcription Factors; D020134:Catalytic Domain / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins; D008239:Lysine / Q000378:metabolism; D046911:Macromolecular Substances; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D017434:Protein Structure, Tertiary / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; C470285:MET30 protein, S cerevisiae; C073675:MET4 protein, S cerevisiae; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D011108:Polymers; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008239:Lysine