A minimal glycine-alanine repeat prevents the interaction of ubiquitinated I kappaB alpha with the proteasome: a new mechanism for selective inhibition of proteolysis.
The Epstein-Barr virus nuclear antigen 1 contains a glycine-alanine repeat that inhibits in cis MHC class I-restricted presentation. We report here that insertion of a minimal glycine-alanine repeat motif in different positions of I kappaB alpha protects this NF-kappaB inhibitor from signal-induced degradation dependent on ubiquitin-proteasome, and decreases its basal turnover in vivo resulting in constitutive dominant-negative mutants. The chimeras are phosphorylated and ubiquitinated in response to tumor necrosis factor alpha, but are then released from NF-kappaB and fail to associate with the proteasome. This explains how functionally competent I kappaB alpha is protected from proteasomal disruption and identifies the glycine-alanine repeat as a new regulator of proteolysis.
Microbiology and Tumor Biology Center, Karolinska Institute, Stockholm, Sweden.
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Sharipo
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Imreh
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Leonchiks
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Imreh
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Masucci
D000595:Amino Acid Sequence; D017209:Apoptosis; D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004151:Dipeptides; D005799:Genes, Dominant; D006031:Glycosylation; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D007700:Kinetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D046988:Proteasome Endopeptidase Complex; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D014452:Ubiquitins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004151:Dipeptides; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011994:Recombinant Proteins; D014452:Ubiquitins; D000072000:NF-KappaB Inhibitor alpha; C065992:N-glycylalanine; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex