GRG5/AES interacts with T-cell factor 4 (TCF4) and downregulates Wnt signaling in human cells and zebrafish embryos

PLoS One. 2013 Jul 1;8(7):e67694. doi: 10.1371/journal.pone.0067694. Print 2013.

Abstract

Transcriptional control by TCF/LEF proteins is crucial in key developmental processes such as embryo polarity, tissue architecture and cell fate determination. TCFs associate with β-catenin to activate transcription in the presence of Wnt signaling, but in its absence act as repressors together with Groucho-family proteins (GRGs). TCF4 is critical in vertebrate intestinal epithelium, where TCF4-β-catenin complexes are necessary for the maintenance of a proliferative compartment, and their abnormal formation initiates tumorigenesis. However, the extent of TCF4-GRG complexes' roles in development and the mechanisms by which they repress transcription are not completely understood. Here we characterize the interaction between TCF4 and GRG5/AES, a Groucho family member whose functional relationship with TCFs has been controversial. We map the core GRG interaction region in TCF4 to a 111-amino acid fragment and show that, in contrast to other GRGs, GRG5/AES-binding specifically depends on a 4-amino acid motif (LVPQ) present only in TCF3 and some TCF4 isoforms. We further demonstrate that GRG5/AES represses Wnt-mediated transcription both in human cells and zebrafish embryos. Importantly, we provide the first evidence of an inherent repressive function of GRG5/AES in dorsal-ventral patterning during early zebrafish embryogenesis. These results improve our understanding of TCF-GRG interactions, have significant implications for models of transcriptional repression by TCF-GRG complexes, and lay the groundwork for in depth direct assessment of the potential role of Groucho-family proteins in both normal and abnormal development.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Co-Repressor Proteins / genetics
  • Co-Repressor Proteins / metabolism*
  • Down-Regulation
  • Gene Expression Regulation, Developmental
  • HEK293 Cells
  • Humans
  • Protein Interaction Maps
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Signal Transduction
  • Transcription Factor 7-Like 2 Protein / chemistry
  • Transcription Factor 7-Like 2 Protein / genetics
  • Transcription Factor 7-Like 2 Protein / metabolism*
  • Transcriptional Activation*
  • Up-Regulation
  • Wnt Proteins / genetics
  • Wnt Proteins / metabolism*
  • Zebrafish / embryology*
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*
  • beta Catenin / genetics
  • beta Catenin / metabolism

Substances

  • Co-Repressor Proteins
  • Repressor Proteins
  • TLE5 protein, human
  • Transcription Factor 7-Like 2 Protein
  • Wnt Proteins
  • Zebrafish Proteins
  • beta Catenin
  • tle5 protein, zebrafish

Grant support

This work was supported by Fundação para a Ciência e a Tecnologia (through grants POCTI/41854/MGI/2001 and Ciência2008-ICAAM to L.T.C., SFRH/BD/24402/2005 to Â.M.S.C. and SFRH/BD/44264/2008 to I.P.-C. and Strategic Project PEst-C/AGR/UI0115/2011) as well as FEDER Funds through the COMPETE programme. IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology and Higher Education and is partially supported by FCT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.