Enhancer cooperativity as a novel mechanism underlying the transcriptional regulation of E-cadherin during mesenchymal to epithelial transition

Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) highlight crucial steps during embryogenesis and tumorigenesis. Induction of dramatic changes in gene expression and cell features is reflected by modulation of Cdh1 (E-cadherin) expression. We show that Cdh1 activity during MET is governed by two enhancers at + 7.8 kb and at + 11.5 kb within intron 2 that are activated by binding of Grhl3 and Hnf4 alpha, respectively. Recruitment of Grhl3 and Hnf4 alpha to the enhancers is crucial for activating Cdh1 and accomplishing MET in non-tumorigenic mouse mammary gland cells (NMuMG). Moreover, the two enhancers cooperate via Grhl3 and Hnf4 alpha binding, induction of DNA-looping and clustering at the promoter to orchestrate E-cadherin re-expression. Our results provide novel insights into the cellular mechanisms whereby cells respond to MET signals and re-establish an epithelial phenotype by enhancer cooperativity. A general importance of our findings including MET-mediated colonization of metastasizing tumor cells is suggested. (C) 2015 Elsevier B.V. All rights reserved