Identification of a motif within the 5' regulatory region of pS2 which is responsible for AP-1 binding and TCDD-mediated suppression

Biochemistry. 1997 May 20;36(20):6080-9. doi: 10.1021/bi962131b.


2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related compounds modulate several endocrine systems by altering hormone synthesis, enhancing ligand metabolism, and down-regulating receptor levels/binding activity. Previous studies have demonstrated that TCDD inhibits the 17beta-estradiol (E2)-induction of pS2, a human breast cancer prognostic marker. This inhibition occurs at the gene expression level and is Ah receptor (AhR)-mediated. Analysis of the 5' regulatory region has identified three motifs which resemble dioxin response element (DRE) core sequences. pS2-regulated luciferase deletion constructs identified the DRE-like motif located at -527 to -514 as being required for TCDD-mediated suppression. A point mutation within this core motif (T-518C) abolished the inhibition by TCDD while UV-induced protein-DNA cross-linking and competitive gel retardation assays demonstrated AhR complex binding to this motif. Further study of this region also revealed an adjacent putative AP-1 site, diverging by one base pair from the consensus sequence. Gel retardation assays using TPA-treated MCF-7 cell nuclear extracts showed an induced complex binding to the AP-1-like site. Competition studies and antibody supershifts confirmed that the retarded complex consists of AP-1-like proteins. pS2-regulated luciferase constructs containing mutations specific to the AP-1-like motif greatly diminished the inducibility in response to E2. These results suggest that an interaction between AhR complexes and AP-1-like proteins may be responsible for TCDD-mediated inhibition of E2-induced pS2 expression.

Publication types

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

MeSH terms

  • Base Sequence
  • Breast Neoplasms / genetics*
  • DNA Mutational Analysis
  • DNA-Binding Proteins / metabolism
  • Estradiol / pharmacology
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Molecular Sequence Data
  • Polychlorinated Dibenzodioxins / pharmacology*
  • Protein Binding
  • Proteins / genetics*
  • Receptors, Aryl Hydrocarbon / metabolism
  • Receptors, Estrogen / metabolism
  • Regulatory Sequences, Nucleic Acid*
  • Sequence Deletion
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factor AP-1 / metabolism*
  • Trefoil Factor-1
  • Tumor Cells, Cultured
  • Tumor Suppressor Proteins


  • DNA-Binding Proteins
  • Polychlorinated Dibenzodioxins
  • Proteins
  • Receptors, Aryl Hydrocarbon
  • Receptors, Estrogen
  • TFF1 protein, human
  • Transcription Factor AP-1
  • Trefoil Factor-1
  • Tumor Suppressor Proteins
  • Estradiol
  • Tetradecanoylphorbol Acetate