Activation of the IkappaB kinase complex by TRAF6 requires a dimeric ubiquitin-conjugating enzyme complex and a unique polyubiquitin chain.
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.
Deng
L
L
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas 75390, USA.
Wang
C
C
Spencer
E
E
Yang
L
L
Braun
A
A
You
J
J
Slaughter
C
C
Pickart
C
C
Chen
Z J
ZJ
D000595:Amino Acid Sequence; D001704:Biopolymers / Q000378:metabolism*; D002474:Cell-Free System; D003001:Cloning, Molecular; D019281:Dimerization; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D008025:Ligases / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D025821:Polyubiquitin; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D048029:TNF Receptor-Associated Factor 6; D014157:Transcription Factors; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism*
D001704:Biopolymers; D011506:Proteins; D048029:TNF Receptor-Associated Factor 6; D014157:Transcription Factors; D014452:Ubiquitins; D025821:Polyubiquitin; C471624:UBE2V1 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D008025:Ligases