NF-kappa B/Rel family members are physically associated phosphoproteins

Biochem J. 1994 Oct 15;303 ( Pt 2)(Pt 2):499-506. doi: 10.1042/bj3030499.


We performed radioimmunoprecipitation followed by serial immunoblots to show that, in the unstimulated Jurkat T cell line, the NF-kappa B/Rel family proteins, p80-c-Rel, p105-NF-kappa B, p65-NF-kappa B, p50-NF-kappa B and p36-I kappa B alpha, can be detected as complexes using antisera against c-Rel, p105-NF-kappa B or p65-NF-kappa B. p36-I kappa B alpha and p105, both known inhibitors of NF-kappa B function, can physically associate with NF-kappa B/Rel family members, but not with each other. In vivo and in vitro phosphorylation experiments demonstrated that NF-kappa B/Rel family members, including p105, c-Rel, p50, p65 (for the first time for p50 and p65) and p36-I kappa B alpha are also phosphoproteins. Phosphoserine and phosphothreonine residues were identified in these proteins isolated from unstimulated Jurkat cells. Both unphosphorylated and hyperphosphorylated forms of p36-I kappa B alpha were found in the complexes, suggesting that hyperphosphorylated I kappa B alpha is still capable of associating with the NF-kappa B/Rel family members. After stimulation with phorbol 12-myristate 13-acetate and phytohaemagglutinin for 10 min, p105-NF-kappa B and p50-NF-kappa B, but not p36-I kappa B, were highly phosphorylated. Phosphopeptide mapping of p105 showed that phorbol ester/phytohaemagglutinin stimulation may change p105 phosphorylation qualitatively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Line
  • Cross Reactions
  • Electrophoresis, Polyacrylamide Gel
  • Immune Sera / immunology
  • Molecular Weight
  • NF-kappa B / chemistry*
  • NF-kappa B / immunology
  • NF-kappa B / metabolism
  • Peptide Mapping
  • Phosphorylation
  • Proto-Oncogene Proteins / chemistry*
  • Proto-Oncogene Proteins / immunology
  • Proto-Oncogene Proteins / metabolism
  • Radioimmunoprecipitation Assay
  • T-Lymphocytes / drug effects
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factor RelB
  • Transcription Factors*


  • Immune Sera
  • NF-kappa B
  • Proto-Oncogene Proteins
  • Transcription Factors
  • Transcription Factor RelB
  • Tetradecanoylphorbol Acetate