The nuclear factor kappa B (NF-κB) transcription factor-mediated transcription is the endpoint of a series of signal transduction events that are initiated by a vast array of stimuli. Both the proteolytic and non-proteolytic functions of ubiquitination are critically important for the regulation of NF-κB activation. Lys63-linked polyubiquitination of TAK1 is required for IL-1β-induced IKK/NF-κB activation. However, the lysine site that mediates Lys63-linked TAK1 polyubiquitination in IL-1β signaling is still controversial. Here we report that TAK1 Lysine 158 but not Lysine 209 is required for IL-1β-induced Lys63-linked TAK1 polyubiquitination and TAK1-mediated IKK, JNK, and p38 activation. Co-overexpression of TAK1 wild-type and K209R mutant with TAB1 induced Lys63-linked TAK1 polyubiquitination and NF-κB activation whereas TAK1 K158R mutant failed to do so. Furthermore, IL-1β induces polyubiquitination of TAK1 wild-type and K209R mutant but not K158R mutant. Reconstitution of TAK1-deficient mouse embryo fibroblast cells with wild-type, K158R mutant, or K209R mutant TAK1 reveals that TAK1 Lys-158 but not Lys-209 is required for IL-1β-induced IKK, p38 and JNK activation.
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