TIFA activates IκB kinase (IKK) by promoting oligomerization and ubiquitination of TRAF6

Chee Kwee Ea, Lijun Sun, Jun Ichiro Inoue, Zhijian J. Chen

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


TRAF6 (tumor necrosis factor receptor-associated factor 6) is a RING (really interesting new gene) domain ubiquitin (Ub) ligase that mediates the activation of protein kinases, such as transforming growth factor β-activated kinase (TAK1) and IκB kinase (IKK), by catalyzing the formation of a unique polyubiquitin chain linked through Lys-63 of Ub. Here, we present evidence that TIFA (TRAF-interacting protein with a forkhead-associated domain, also known as T2BP) activates IKK by promoting the oligomerization and Ub ligase activity of TRAF6. We show that recombinant TIFA protein, but not TRAF6-binding-defective mutant, can activate IKK in crude cytosolic extracts. Furthermore, TIFA activates IKK in an in vitro reconstitution system consisting of purified proteins, including TRAF6, the TAK1 kinase complex, and Ub-conjugating enzyme complex Ubc13-Uev1A. Interestingly, a fraction of recombinant TIFA protein exists as high-molecular-weight oligomers, and only these oligomeric forms of TIFA can activate IKK. Importantly, TIFA induces the oligomerization and polyubiquitination of TRAF6, which leads to the activation of TAK1 and IKK through a proteasome-independent mechanism.

Original languageEnglish (US)
Pages (from-to)15318-15323
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number43
StatePublished - Oct 26 2004

ASJC Scopus subject areas

  • General


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