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Sensing of Lys 63-linked polyubiquitination by NEMO is a key event in NF-kappaB activation [corrected].

The transcription factor NF-kappaB is sequestered in the cytoplasm in a complex with IkappaB. Almost all NF-kappaB activation pathways converge on IkappaB kinase (IKK), which phosphorylates IkappaB resulting in Lys 48-linked polyubiquitination of IkappaB and its degradation. This allows migration of NF-kappaB to the nucleus where it regulates gene expression. IKK has two catalytic subunits, IKKalpha and IKKbeta, and a regulatory subunit, IKKgamma or NEMO. NEMO is essential for NF-kappaB activation, and NEMO dysfunction in humans is the cause of incontinentia pigmenti and hypohidrotic ectodermal dysplasia and immunodeficiency (HED-ID). The recruitment of IKK to occupied cytokine receptors, and its subsequent activation, are dependent on the attachment of Lys 63-linked polyubiquitin chains to signalling intermediates such as receptor-interacting protein (RIP). Here, we show that NEMO binds to Lys 63- but not Lys 48-linked polyubiquitin, and that single point mutations in NEMO that prevent binding to Lys 63-linked polyubiquitin also abrogates the binding of NEMO to RIP in tumour necrosis factor (TNF)-alpha-stimulated cells, the recruitment of IKK to TNF receptor (TNF-R) 1, and the activation of IKK and NF-kappaB. RIP is also destabilized in the absence of NEMO binding and undergoes proteasomal degradation in TNF-alpha-treated cells. These results provide a mechanism for NEMO's critical role in IKK activation, and a key to understanding the link between cytokine-receptor proximal signalling and IKK and NF-kappaB activation.

Pubmed ID: 16547522


  • Wu CJ
  • Conze DB
  • Li T
  • Srinivasula SM
  • Ashwell JD


Nature cell biology

Publication Data

April 11, 2006

Associated Grants

  • Agency: Intramural NIH HHS, Id:

Mesh Terms

  • Biosensing Techniques
  • Electrophoretic Mobility Shift Assay
  • HeLa Cells
  • Humans
  • I-kappa B Kinase
  • Immunoprecipitation
  • Lysine
  • NF-kappa B
  • Point Mutation
  • Protein-Serine-Threonine Kinases
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Receptors, Tumor Necrosis Factor, Type I
  • Saccharomyces cerevisiae
  • Signal Transduction
  • Tumor Necrosis Factor Receptor-Associated Peptides and Proteins
  • Tumor Necrosis Factor-alpha
  • Two-Hybrid System Techniques
  • Ubiquitin