Proteolysis-independent regulation of the transcription factor Met4 by a single Lys 48-linked ubiquitin chain
Related Experiment Video
Updated: Aug 23, 2026

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones
Published on: July 25, 2019
Karin Flick1, Ikram Ouni, James A Wohlschlegel
1Department of Biological Chemistry, University of California Irvine, Irvine, CA 92697, USA.
Abstract:
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.
Related Concept Videos
Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Regulation of Expression at Multiple Steps
The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
RNA Polymerase II Accessory Proteins

