C-terminal-binding protein directly activates and represses Wnt transcriptional targets in Drosophila

EMBO J. 2006 Jun 21;25(12):2735-45. doi: 10.1038/sj.emboj.7601153. Epub 2006 May 18.

Abstract

Regulation of Wnt transcriptional targets is thought to occur by a transcriptional switch. In the absence of Wnt signaling, sequence-specific DNA-binding proteins of the TCF family repress Wnt target genes. Upon Wnt stimulation, stabilized beta-catenin binds to TCFs, converting them into transcriptional activators. C-terminal-binding protein (CtBP) is a transcriptional corepressor that has been reported to inhibit Wnt signaling by binding to TCFs or by preventing beta-catenin from binding to TCF. Here, we show that CtBP is also required for the activation of some Wnt targets in Drosophila. CtBP is recruited to Wnt-regulated enhancers in a Wnt-dependent manner, where it augments Armadillo (the fly beta-catenin) transcriptional activation. We also found that CtBP is required for repression of a subset of Wnt targets in the absence of Wnt stimulation, but in a manner distinct from previously reported mechanisms. CtBP binds to Wnt-regulated enhancers in a TCF-independent manner and represses target genes in parallel with TCF. Our data indicate dual roles for CtBP as a gene-specific activator and repressor of Wnt target gene transcription.

Publication types

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

MeSH terms

  • Alcohol Oxidoreductases
  • Animals
  • Armadillo Domain Proteins / metabolism
  • Cells, Cultured
  • DNA-Binding Proteins / deficiency
  • DNA-Binding Proteins / metabolism*
  • Drosophila / cytology
  • Drosophila / genetics*
  • Drosophila / metabolism*
  • Drosophila Proteins / metabolism
  • Enhancer Elements, Genetic
  • Eye / cytology
  • Models, Biological
  • Phosphoproteins / deficiency
  • Phosphoproteins / metabolism*
  • Protein Binding
  • Repressor Proteins / metabolism*
  • Signal Transduction
  • TCF Transcription Factors / metabolism
  • Trans-Activators / deficiency
  • Trans-Activators / metabolism*
  • Transcription Factors / metabolism
  • Transcription, Genetic*
  • Transcriptional Activation / genetics
  • Wnt Proteins / metabolism*

Substances

  • ARM protein, Drosophila
  • Armadillo Domain Proteins
  • DNA-Binding Proteins
  • Drosophila Proteins
  • Phosphoproteins
  • Repressor Proteins
  • TCF Transcription Factors
  • Trans-Activators
  • Transcription Factors
  • Wnt Proteins
  • Alcohol Oxidoreductases
  • C-terminal binding protein