The rel-associated pp40 protein prevents DNA binding of Rel and NF-kappa B: relationship with I kappa B beta and regulation by phosphorylation

Genes Dev. 1991 Aug;5(8):1464-76. doi: 10.1101/gad.5.8.1464.


The product of proto-oncogene Rel associates with a number of cellular proteins. We have studied the effect of one of them, a phosphoprotein of 40 kD (pp40), on the DNA-binding activity of the Rel protein. We demonstrate that purified pp40 not only inhibits the binding of Rel, but also NF-kappa B (p50-p65) heterocomplex to DNA. Additionally, I kappa B beta, but not I kappa B alpha, also prevented the binding of Rel to the kappa B site. I kappa B beta and pp40 are related proteins because (1) they share a number of common tryptic peptides, (2) their inhibitory effect on DNA binding can be abolished by preincubation with pp40-specific antiserum, and (3) labeled I kappa B beta can be immunoprecipitated with pp40 antibodies. pp40 is part of the Rel complex present in the cytoplasm and nuclear extracts of WEHI-231 cells. The activity of pp40 to inhibit the DNA binding of Rel and NF-kappa B is modulated by phosphorylation.

Publication types

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

MeSH terms

  • Animals
  • Base Sequence
  • Binding Sites
  • Cell Line
  • Cell Transformation, Neoplastic
  • DNA-Binding Proteins / metabolism*
  • Enhancer Elements, Genetic
  • Homeostasis
  • Immunoglobulin kappa-Chains / genetics
  • Mice
  • Molecular Sequence Data
  • NF-kappa B / metabolism*
  • Oligonucleotide Probes
  • Peptide Fragments / isolation & purification
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Protein Kinase C / metabolism
  • Protein Kinases / metabolism
  • Protein-Tyrosine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-rel
  • Proto-Oncogenes
  • Repressor Proteins / metabolism*


  • DNA-Binding Proteins
  • Immunoglobulin kappa-Chains
  • NF-kappa B
  • Oligonucleotide Probes
  • Peptide Fragments
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-rel
  • Repressor Proteins
  • Protein Kinases
  • Protein-Tyrosine Kinases
  • Protein Kinase C