Signal-induced degradation of I(kappa)B(alpha): association with NF-kappaB and the PEST sequence in I(kappa)B(alpha) are not required.
Signal-induced degradation of I(kappa)B(alpha) via the ubiquitin-proteasome pathway requires phosphorylation on residues serine 32 and serine 36 followed by ubiquitination on lysines 21 and 22. We investigated the role of other regions of I(kappa)B(alpha) which may be involved in its degradation. Here we report that the carboxy-terminal PEST sequence is not required for I(kappa)B(alpha) signal-induced degradation. However, removal of the PEST sequence stabilizes free I(kappa)B(alpha) in unstimulated cells. We further report that a PEST deletion mutant does not associate well with NF-(kappa)B proteins but is degraded in response to signal. Therefore, we conclude that both association with NF-(kappa)B and a PEST sequence are not required for signal-induced I(kappa)B(alpha) degradation. Additionally, the PEST sequence may be required for constitutive turnover of free I(kappa)B(alpha).
Laboratory of Genetics, The Salk Institute, San Diego, California 92186, USA.
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D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D007668:Kidney; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014452:Ubiquitins / Q000378:metabolism
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D010750:Phosphoproteins; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D014452:Ubiquitins; D000072000:NF-KappaB Inhibitor alpha; C077938:cact protein, Drosophila; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex