title: Enhancer decommissioning by Snail1-induced competitive displacement of TCF7L2 and down-regulation of transcriptional activators results in EPHB2 silencing.
abstract: Transcriptional silencing is a major cause for the inactivation of tumor suppressor genes, however, the underlying mechanisms are only poorly understood. The EPHB2 gene encodes a receptor tyrosine kinase that controls epithelial cell migration and allocation in intestinal crypts. Through its ability to restrict cell spreading, EPHB2 functions as a tumor suppressor in colorectal cancer whose expression is frequently lost as tumors progress to the carcinoma stage. Previously we reported that EPHB2 expression depends on a transcriptional enhancer whose activity is diminished in EPHB2 non-expressing cells. Here we investigated the mechanisms that lead to EPHB2 enhancer inactivation. We show that expression of EPHB2 and SNAIL1 - an inducer of epithelial-mesenchymal transition (EMT) - is anti-correlated in colorectal cancer cell lines and tumors. In a cellular model of Snail1-induced EMT, we observe that features of active chromatin at the EPHB2 enhancer are diminished upon expression of murine Snail1. We identify the transcription factors FOXA1, MYB, CDX2 and TCF7L2 as EPHB2 enhancer factors and demonstrate that Snail1 indirectly inactivates the EPHB2 enhancer by downregulation of FOXA1 and MYB. In addition, Snail1 induces the expression of Lymphoid enhancer factor 1 (LEF1) which competitively displaces TCF7L2 from the EPHB2 enhancer. In contrast to TCF7L2, however, LEF1 appears to repress the EPHB2 enhancer. Our findings underscore the importance of transcriptional enhancers for gene regulation under physiological and pathological conditions and show that SNAIL1 employs a combinatorial mechanism to inactivate the EPHB2 enhancer based on activator deprivation and competitive displacement of transcription factors.
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany; Department of Cellular and Molecular Immunology, Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, D-79108 Freiburg, Germany; Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
authors: Oskar
authors: O
authors: Schnappauf
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
authors: Sven
authors: S
authors: Beyes
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany.
authors: Annika
authors: A
authors: Dertmann
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany.
authors: Vivien
authors: V
authors: Freihen
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany.
authors: Patrick
authors: P
authors: Frey
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany.
authors: Sabine
authors: S
authors: Jägle
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany.
authors: Katja
authors: K
authors: Rose
authors: The Roslin Institute, The University of Edinburgh, Easter Bush, Midlothian EH25 9RG, Scotland, UK.
authors: Tom
authors: T
authors: Michoel
authors: Department of Cellular and Molecular Immunology, Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, D-79108 Freiburg, Germany.
authors: Rudolf
authors: R
authors: Grosschedl
authors: Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 17, D-79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 18, D-79104 Freiburg, Germany. Electronic address: andreas.hecht@mol-med.uni-freiburg.de.
authors: Andreas
authors: A
authors: Hecht
mesh_terms: D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D020868:Gene Silencing; D006801:Humans; D036183:Receptor, EphB2 / Q000235:genetics*; D000071250:Snail Family Transcription Factors / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism*; D058118:Transcription Factor 7-Like 2 Protein / Q000378:metabolism*
chemical_list: D002843:Chromatin; C000604407:SNAI1 protein, human; D000071250:Snail Family Transcription Factors; C544894:TCF7L2 protein, human; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; C586310:EPHB2 protein, human; D036183:Receptor, EphB2
keywords: EPHB2; Epithelial-mesenchymal transition; FOXA1; LEF1; MYB; Transcriptional enhancer