HTLV-I Tax protein binds to MEKK1 to stimulate IkappaB kinase activity and NF-kappaB activation

Cell. 1998 May 29;93(5):875-84. doi: 10.1016/s0092-8674(00)81447-6.


NF-kappaB, a key regulator of the cellular inflammatory and immune response, is activated by the HTLV-I transforming and transactivating protein Tax. We show that Tax binds to the amino terminus of the protein kinase MEKK1, a component of an IkappaB kinase complex, and stimulates MEKK1 kinase activity. Tax expression increases the activity of IkappaB kinase beta (IKKbeta) to enhance phosphorylation of serine residues in IkappaB alpha that lead to its degradation. Dominant negative mutants of both IKKbeta and MEKK1 prevent Tax activation of the NF-kappaB pathway. Furthermore, recombinant MEKK1 stimulates IKKbeta phosphorylation of IkappaB alpha. Thus, Tax-mediated increases in NF-kappaB nuclear translocation result from direct interactions of Tax and MEKK1 leading to enhanced IKKbeta phosphorylation of IkappaB alpha.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • COS Cells
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation
  • Gene Expression Regulation
  • Gene Products, tax / metabolism*
  • HeLa Cells
  • Human T-lymphotropic virus 1*
  • Humans
  • I-kappa B Kinase
  • I-kappa B Proteins*
  • MAP Kinase Kinase Kinase 1*
  • Mutation
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism*
  • Phosphorylation
  • Precipitin Tests
  • Protein Binding
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • Signal Transduction
  • Transfection


  • DNA-Binding Proteins
  • Gene Products, tax
  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • NF-KappaB Inhibitor alpha
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases
  • CHUK protein, human
  • I-kappa B Kinase
  • IKBKB protein, human
  • IKBKE protein, human
  • MAP Kinase Kinase Kinase 1
  • MAP3K1 protein, human