Estrogen induces c-myc gene expression via an upstream enhancer activated by the estrogen receptor and the AP-1 transcription factor

Mol Endocrinol. 2011 Sep;25(9):1527-38. doi: 10.1210/me.2011-1037. Epub 2011 Aug 11.

Abstract

c-myc oncogene is implicated in tumorigenesis of many cancers, including breast cancer. Although c-myc is a well-known estrogen-induced gene, its promoter has no estrogen-response element, and the underlying mechanism by which estrogen induces its expression remains obscure. Recent genome-wide studies by us and others suggested that distant elements may mediate estrogen induction of gene expression. In this study, we investigated the molecular mechanism by which estrogen induces c-myc expression with a focus on these distal elements. Estrogen rapidly induced c-myc expression in estrogen receptor (ER)-positive breast cancer cells. Although estrogen had little effect on c-myc proximal promoter activity, it did stimulate the activity of a luciferase reporter containing a distal 67-kb enhancer. Estrogen induction of this luciferase reporter was dependent upon both a half-estrogen response element and an activator protein 1 (AP-1) site within this enhancer, which are conserved across 11 different mammalian species. Small interfering RNA experiments and chromatin immunoprecipitation assays demonstrated the necessity of ER and AP-1 cross talk for estrogen to induce c-myc expression. TAM67, the AP-1 dominant negative, partially inhibited estrogen induction of c-myc expression and suppressed estrogen-induced cell cycle progression. Together, these results demonstrate a novel pathway of estrogen regulation of gene expression by cooperation between ER and AP-1 at the distal enhancer element and that AP-1 is involved in estrogen induction of the c-myc oncogene. These results solve the long-standing question in the field of endocrinology of how estrogen induces c-myc expression.

Publication types

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

MeSH terms

  • Base Sequence
  • Binding Sites
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • CREB-Binding Protein / metabolism
  • Cell Cycle / drug effects
  • Cell Cycle / genetics
  • Cell Line, Tumor
  • Chromatin Immunoprecipitation
  • E1A-Associated p300 Protein / metabolism
  • Enhancer Elements, Genetic / genetics*
  • Estrogens / pharmacology*
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Gene Knockdown Techniques
  • Humans
  • Luciferases / metabolism
  • Models, Biological
  • Molecular Sequence Data
  • Protein Binding / drug effects
  • Proto-Oncogene Proteins c-myc / genetics*
  • Proto-Oncogene Proteins c-myc / metabolism
  • RNA, Small Interfering / metabolism
  • Receptors, Estrogen / metabolism*
  • Response Elements / genetics
  • Sequence Deletion / genetics
  • Sp1 Transcription Factor / metabolism
  • Transcription Factor AP-1 / metabolism*

Substances

  • Estrogens
  • Proto-Oncogene Proteins c-myc
  • RNA, Small Interfering
  • Receptors, Estrogen
  • Sp1 Transcription Factor
  • Transcription Factor AP-1
  • Luciferases
  • CREB-Binding Protein
  • E1A-Associated p300 Protein
  • Ep300 protein, mouse