Abstract
TRAF6 is a signal transducer in the NF-kappaB pathway that activates IkappaB kinase (IKK) in response to proinflammatory cytokines. We have purified a heterodimeric protein complex that links TRAF6 to IKK activation. Peptide mass fingerprinting analysis reveals that this complex is composed of the ubiquitin conjugating enzyme Ubc13 and the Ubc-like protein Uev1A. We find that TRAF6, a RING domain protein, functions together with Ubc13/Uev1A to catalyze the synthesis of unique polyubiquitin chains linked through lysine-63 (K63) of ubiquitin. Blockade of this polyubiquitin chain synthesis, but not inhibition of the proteasome, prevents the activation of IKK by TRAF6. These results unveil a new regulatory function for ubiquitin, in which IKK is activated through the assembly of K63-linked polyubiquitin chains.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Biopolymers / metabolism*
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Cell-Free System
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Cloning, Molecular
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Dimerization
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Enzyme Activation
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HeLa Cells
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Humans
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I-kappa B Kinase
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Ligases / isolation & purification
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Ligases / metabolism*
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Molecular Sequence Data
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Peptide Mapping
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Polyubiquitin
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Protein Serine-Threonine Kinases / metabolism*
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Proteins / metabolism*
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Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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TNF Receptor-Associated Factor 6
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Transcription Factors*
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Ubiquitin-Conjugating Enzymes
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Ubiquitin-Protein Ligases
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Ubiquitins / metabolism*
Substances
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Biopolymers
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Proteins
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TNF Receptor-Associated Factor 6
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Transcription Factors
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Ubiquitins
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Polyubiquitin
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UBE2V1 protein, human
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Ubiquitin-Conjugating Enzymes
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Ubiquitin-Protein Ligases
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Protein Serine-Threonine Kinases
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CHUK protein, human
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I-kappa B Kinase
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IKBKB protein, human
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IKBKE protein, human
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Ligases