title: SUMO-1 modification of IkappaBalpha inhibits NF-kappaB activation.
abstract: 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.
authors.affiliation: School of Biomedical Science, University of St. Andrews, Fife, United Kingdom.
authors.forename: J M
authors.initials: JM
authors.lastname: Desterro
authors.forename: M S
authors.initials: MS
authors.lastname: Rodriguez
authors.forename: R T
authors.initials: RT
authors.lastname: Hay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004274:DNA, Recombinant / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D020672:I-kappa B Proteins; D007375:Interleukin-1 / Q000494:pharmacology; D046911:Macromolecular Substances; D009097:Multienzyme Complexes / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011994:Recombinant Proteins / Q000494:pharmacology; D025842:SUMO-1 Protein; D015398:Signal Transduction; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: D004274:DNA, Recombinant; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D007375:Interleukin-1; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011994:Recombinant Proteins; D025842:SUMO-1 Protein; D014409:Tumor Necrosis Factor-alpha; D014452:Ubiquitins; D000072000:NF-KappaB Inhibitor alpha; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex