The ubiquitin ligase TRAF6 is essential for the activation of NF-κB and MAP kinases in several signalling pathways important for a range of cellular processes including immune function. TRAF6 functions together with a ubiquitin-conjugating enzyme complex to activate the TAK1 kinase complex downstream, which in turn leads to the activation of NF-κB. Here, by reconstituting TAK1 activation in vitro, free Lys 63 polyubiquitin chains are shown to activate TAK1 directly.
- Zong-Ping Xia
- Lijun Sun
- Zhijian J. Chen