Identification of HTF (HER2 transcription factor) as an AP-2 (activator protein-2) transcription factor and contribution of the HTF binding site to ERBB2 gene overexpression

Biochem J. 2003 Feb 15;370(Pt 1):323-9. doi: 10.1042/BJ20021238.

Abstract

The ERBB2 gene is overexpressed in 30% of human breast cancers and this is correlated with poor prognosis. Overexpression of the ERBB2 gene is due to increased transcription and gene amplification. Our previous studies have identified a new cis element in the ERBB2 promoter which is involved in the gene's overexpression. This cis element, located 501 bp upstream from the main ERBB2 transcription initiation site, binds a transcription factor called HTF (HER2 transcription factor). We report here the identification of HTF as an AP-2 (activator protein-2) transcription factor. The new cis element is bound by AP-2 with high affinity, compared with a previously described AP-2 binding site located 284 bp downstream. Co-transfection of an AP-2alpha expression vector with a reporter vector containing the newly identified AP-2 binding site in front of a minimal ERBB2 promoter induced a dose-dependent increase in transcriptional activity. We examined the contribution of the new AP-2 binding site to ERBB2 overexpression. For this purpose we abolished the new and/or the previously described AP-2 binding sequence by site-directed mutagenesis. The results show that the two functional AP-2 sites in the first 700 bp of the ERBB2 promoter co-operate to achieve maximal transcriptional activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Binding Sites
  • DNA Primers
  • DNA-Binding Proteins / metabolism*
  • Humans
  • Mutagenesis, Site-Directed
  • Promoter Regions, Genetic
  • Receptor, ErbB-2 / genetics
  • Receptor, ErbB-2 / metabolism*
  • Sequence Homology, Nucleic Acid
  • Transcription Factor AP-2
  • Transcription Factors / metabolism*
  • Tumor Cells, Cultured

Substances

  • DNA Primers
  • DNA-Binding Proteins
  • TFAP2A protein, human
  • Transcription Factor AP-2
  • Transcription Factors
  • Receptor, ErbB-2