Degradation of transcription factor IRF-1 by the ubiquitin-proteasome pathway. The C-terminal region governs the protein stability

Eur J Biochem. 2000 Mar;267(6):1680-6. doi: 10.1046/j.1432-1327.2000.01163.x.


Interferon regulatory factor-1(IRF-1) is a transcriptional activator of interferon genes and interferon-inducible genes. It has been shown that IRF-1 functions not only as a regulator of the interferon-responsive system but also as a regulator of cell growth and apoptosis. In addition, it is known that IRF-1 is a short-lived protein, but the mechanism that regulates its stability has not yet been clarified. Here, we show that IRF-1 is degraded via the ubiquitin-proteasome pathway. IRF-1 protein degradation in HeLa and NIH3T3 cells was inhibited by treatment with proteasome-specific inhibitors. Overexpression of IRF-1 protein and ubiquitin in COS7 cells revealed specific multiubiquitination of IRF-1. Although the full-length IRF-1 was unstable, IRF-1 mutants with C-terminal truncations larger than 39 amino acids were found to be almost stable, suggesting that the 39-residue C-terminal region controls the stability of IRF-1. Further analysis of the stability of a green fluorescent protein-fusion protein containing the 39-residue C-terminal region of IRF-1 showed that this C-terminal region confers instability on green fluorescent protein, a normally stable protein, suggesting that this region functions as a protein-degradation signal. Taking the results together, it can be concluded that the 39-residue C-terminal region is necessary and sufficient to control the stability of the IRF-1 protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Cysteine Endopeptidases / metabolism*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Interferon Regulatory Factor-1
  • Mice
  • Multienzyme Complexes / metabolism*
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / metabolism
  • Peptide Fragments / metabolism
  • Phosphoproteins / chemistry
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Protease Inhibitors / pharmacology
  • Proteasome Endopeptidase Complex
  • Protein Processing, Post-Translational
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / metabolism
  • Sequence Deletion
  • Transfection
  • Ubiquitins / metabolism*


  • DNA-Binding Proteins
  • IRF1 protein, human
  • Interferon Regulatory Factor-1
  • Irf1 protein, mouse
  • Multienzyme Complexes
  • Neoplasm Proteins
  • Peptide Fragments
  • Phosphoproteins
  • Protease Inhibitors
  • Recombinant Fusion Proteins
  • Ubiquitins
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex