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SUMO-1 modification of IkappaBalpha inhibits NF-kappaB activation.

Activation of NF-kappaB is achieved by ubiquitination and proteasome-mediated degradation of IkappaBalpha. We have detected modified IkappaBalpha, conjugated to the small ubiquitin-like protein SUMO-1, which is resistant to signal-induced degradation. In the presence of an E1 SUMO-1-activating enzyme, Ubch9 conjugated SUMO-1 to IkappaBalpha primarily on K21, which is also utilized for ubiquitin modification. Thus, SUMO-1-modified IkappaBalpha cannot be ubiquitinated and is resistant to proteasome-mediated degradation. As a result, overexpression of SUMO-1 inhibits signal-induced activation of NF-kappaB-dependent transcription. Unlike ubiquitin modification, which requires phosphorylation of S32 and S36, SUMO-1 modification of IkappaBalpha is inhibited by phosphorylation. Thus, while ubiquitination targets proteins for rapid degradation, SUMO-1 modification acts antagonistically to generate proteins resistant to degradation.

Pubmed ID: 9734360


  • Desterro JM
  • Rodriguez MS
  • Hay RT


Molecular cell

Publication Data

August 18, 1998

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites
  • Cell Line
  • Cysteine Endopeptidases
  • DNA, Recombinant
  • DNA-Binding Proteins
  • Humans
  • I-kappa B Proteins
  • Interleukin-1
  • Macromolecular Substances
  • Multienzyme Complexes
  • NF-kappa B
  • Proteasome Endopeptidase Complex
  • Recombinant Proteins
  • SUMO-1 Protein
  • Signal Transduction
  • Transcriptional Activation
  • Tumor Necrosis Factor-alpha
  • Ubiquitins