Proteolysis-independent regulation of the transcription factor Met4 by a single Lys 48-linked ubiquitin chain.

Flick K, Ouni I, Wohlschlegel JA, Capati C, McDonald WH, Yates JR, Kaiser P
Nat Cell Biol. 2004 6 (7): 634-41

PMID: 15208638 · DOI:10.1038/ncb1143

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.

MeSH Terms (18)

Basic-Leucine Zipper Transcription Factors Catalytic Domain Cysteine Endopeptidases DNA-Binding Proteins F-Box Proteins Lysine Macromolecular Substances Multienzyme Complexes Peptide Hydrolases Polymers Proteasome Endopeptidase Complex Protein Structure, Tertiary Repressor Proteins Saccharomyces cerevisiae Saccharomyces cerevisiae Proteins Trans-Activators Ubiquitin Ubiquitin-Protein Ligase Complexes

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