The kinase IKKα inhibits activation of the transcription factor NF-κB by phosphorylating the regulatory molecule TAX1BP1


In response to stimulation with proinflammatory cytokines, the deubiquitinase A20 inducibly interacts with the regulatory molecules TAX1BP1, Itch and RNF11 to form the A20 ubiquitin-editing complex. However, the molecular signal that coordinates the assembly of this complex has remained elusive. Here we demonstrate that TAX1BP1 was inducibly phosphorylated on Ser593 and Ser624 in response to proinflammatory stimuli. The kinase IKKα, but not IKKβ, was required for phosphorylation of TAX1BP1 and directly phosphorylated TAX1BP1 in response to stimulation with tumor necrosis factor (TNF) or interleukin 1 (IL-1). TAX1BP1 phosphorylation was pivotal for cytokine-dependent interactions among TAX1BP1, A20, Itch and RNF11 and downregulation of signaling by the transcription factor NF-κB. IKKα therefore serves a key role in the negative feedback of NF-κB canonical signaling by orchestrating assembly of the A20 ubiquitin-editing complex to limit inflammatory gene activation.

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Figure 1: Phosphorylation of TAX1BP1 in response to proinflammatory stimuli.
Figure 2: Phosphorylation of TAX1BP1 on Ser593 and Ser624 in response to stimulation with TNF or IL-1.
Figure 3: Phosphorylation of TAX1BP1 is essential for the termination of NF-κB signaling, Jnk phosphorylation and RIP1 ubiquitination.
Figure 4: Phosphorylation of TAX1BP1 regulates recruitment of the A20 ubiquitin-editing complex to TRAF2 and TRAF6.
Figure 5: Phosphorylation of TAX1BP1 is required for assembly of the A20 ubiquitin-editing complex.
Figure 6: IKKα is essential for assembly of the A20 ubiquitin-editing complex and termination of NF-κB signaling.
Figure 7: Phospho-mimetic TAX1BP1 bypasses the requirement for IKKα in terminating NF-κB signaling.
Figure 8: HTLV-I Tax blocks the phosphorylation of TAX1BP1.


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We thank S. Sun (University of Texas MD Anderson) for hemagglutinin-tagged IKKα, IKKα(K44M), IKKβ and IKKγ (NEMO), and IκBα amino acids 1–54 fused to GST; W. Greene (Gladstone Institute of Virology) for Jurkat Tax Tet-on cells; M. Maeda (Kyoto University) for TL-OM1 cells; M. Birnbaum (University of Pennsylvania) for MEFs doubly deficient in both Akt1 and Akt2; M. Karin (University of California San Diego) for Ikka−/−, Ikbkb−/− and Ikbkg−/− MEFs; E. Androphy (University of Massachusetts) for Flag-TAX1BP1 amino acids 1–789; and J. Leszyk for mass spectrometry and analysis. Supported by the US National Institutes of Health (RO1GM083143 and RO1CA135362 to E.W.H.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute, National Institute of General Medical Sciences or the US National Institutes of Health.

Author information

N.S., R.P. and N.S.H. did experiments and analyzed data; D.W.A. provided reagents and did bioinformatic analyses; and E.W.H. designed and supervised the experiments, analyzed data and wrote the manuscript.

Correspondence to Edward W Harhaj.

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Shembade, N., Pujari, R., Harhaj, N. et al. The kinase IKKα inhibits activation of the transcription factor NF-κB by phosphorylating the regulatory molecule TAX1BP1. Nat Immunol 12, 834–843 (2011).

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