A novel RBP-J kappa-dependent switch from C/EBP beta to C/EBP zeta at the C/EBP binding site on the C-reactive protein promoter

J Immunol. 2007 Jun 1;178(11):7302-9. doi: 10.4049/jimmunol.178.11.7302.

Abstract

Regulation of basal and cytokine (IL-6 and IL-1beta)-induced expression of C-reactive protein (CRP) in human hepatoma Hep3B cells occurs during transcription. A critical transcriptional regulatory element on the CRP promoter is a C/EBP binding site overlapping a NF-kappaB p50 binding site. In response to IL-6, C/EBPbeta and p50 occupy the C/EBP-p50 site on the CRP promoter. The aim of this study was to identify the transcription factors occupying the C/EBP-p50 site in the absence of C/EBPbeta. Accordingly, we treated Hep3B nuclear extract with a C/EBP-binding consensus oligonucleotide to generate an extract lacking active C/EBPbeta. Such treated nuclei contain only C/EBPzeta (also known as CHOP10 and GADD153) because the C/EBP-binding consensus oligonucleotide binds to all C/EBP family proteins except C/EBPzeta. EMSA using this extract revealed formation of a C/EBPzeta-containing complex at the C/EBP-p50 site on the CRP promoter. This complex also contained RBP-Jkappa, a transcription factor known to interact with kappaB sites. RBP-Jkappa was required for the formation of C/EBPzeta-containing complex. The RBP-Jkappa-dependent C/EBPzeta-containing complexes were formed at the C/EBP-p50 site on the CRP promoter in the nuclei of primary human hepatocytes also. In luciferase transactivation assays, overexpressed C/EBPzeta abolished both C/EBPbeta-induced and (IL-6 + IL-1beta)-induced CRP promoter-driven luciferase expression. These results indicate that under basal conditions, C/EBPzeta occupies the C/EBP site, an action that requires RBP-Jkappa. Under induced conditions, C/EBPzeta is replaced by C/EBPbeta and p50. We conclude that the switch between C/EBPbeta and C/EBPzeta participates in regulating CRP transcription. This process uses a novel phenomenon, that is, the incorporation of RBP-Jkappa into C/EBPzeta complexes solely to support the binding of C/EBPzeta to the C/EBP site.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites / genetics
  • Binding Sites / immunology
  • C-Reactive Protein / genetics*
  • C-Reactive Protein / metabolism*
  • CCAAT-Enhancer-Binding Protein-beta / deficiency
  • CCAAT-Enhancer-Binding Protein-beta / genetics
  • CCAAT-Enhancer-Binding Protein-beta / metabolism*
  • CCAAT-Enhancer-Binding Protein-beta / physiology
  • CCAAT-Enhancer-Binding Proteins / biosynthesis
  • CCAAT-Enhancer-Binding Proteins / metabolism*
  • CCAAT-Enhancer-Binding Proteins / physiology
  • Cell Line, Tumor
  • Forkhead Transcription Factors / metabolism
  • Hepatocyte Nuclear Factor 1 / metabolism
  • Humans
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein / metabolism
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein / physiology*
  • Immunoglobulin Switch Region / genetics
  • Immunoglobulin Switch Region / immunology*
  • NF-kappa B p50 Subunit / metabolism
  • Octamer Transcription Factor-1 / metabolism
  • Promoter Regions, Genetic / immunology*
  • Transcription Factor CHOP / biosynthesis
  • Transcription Factor CHOP / metabolism*
  • Transcription Factor CHOP / physiology
  • Transcription, Genetic

Substances

  • CCAAT-Enhancer-Binding Protein-beta
  • CCAAT-Enhancer-Binding Proteins
  • DDIT3 protein, human
  • FOXI1 protein, human
  • Forkhead Transcription Factors
  • Immunoglobulin J Recombination Signal Sequence-Binding Protein
  • NF-kappa B p50 Subunit
  • Octamer Transcription Factor-1
  • RBPJ protein, human
  • Hepatocyte Nuclear Factor 1
  • Transcription Factor CHOP
  • C-Reactive Protein