IKK-i/IKKepsilon controls constitutive, cancer cell-associated NF-kappaB activity via regulation of Ser-536 p65/RelA phosphorylation

J Biol Chem. 2006 Sep 15;281(37):26976-84. doi: 10.1074/jbc.M603133200. Epub 2006 Jul 13.


Nuclear factor kappaB (NF-kappaB) has been studied extensively as an inducible transcriptional regulator of the immune and inflammatory response. NF-kappaB activation downstream of lipopolysaccharide or cytokine stimulation is controlled by the IkappaB kinase complex, which contains IKKalpha and IKKbeta. Significantly, the constitutive activity of NF-kappaB has been implicated as an important aspect of many cancer cells, but mechanisms associated with this activity are poorly understood. An inducible kinase, IKK-i/IKKepsilon, related to the catalytic forms of the IkappaB kinase, has been studied as an anti-viral, innate immune regulator through its ability to control the activity of the transcription factors IRF-3 and IRF-7. Here, we demonstrate that IKK-i/IKKepsilon is expressed in a number of cancer cells and is involved in regulating NF-kappaB activity through its ability to control basal/constitutive, but not cytokine-induced, p65/RelA phosphorylation at Ser-536, a modification proposed to contribute to the transactivation function of NF-kappaB. Knockdown of IKK-i/IKKepsilon or expression of a S536A mutant form of p65 suppresses HeLa cell proliferation. The data indicate a role for IKK-i/IKKepsilon in controlling proliferation of certain cancer cells through regulation of constitutive NF-kappaB activity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Line, Tumor
  • Cell Proliferation
  • Gene Expression Regulation, Neoplastic*
  • HeLa Cells
  • Humans
  • I-kappa B Kinase / metabolism
  • I-kappa B Kinase / physiology*
  • Inflammation
  • NF-kappa B / metabolism*
  • Phosphorylation
  • Promoter Regions, Genetic
  • Serine / chemistry*
  • Transcription Factor RelA / chemistry*


  • NF-kappa B
  • RELA protein, human
  • Transcription Factor RelA
  • Serine
  • I-kappa B Kinase