Unravelling the transcriptional responses of TGF‐β: Smad3 and EZH2 constitute a regulatory switch that controls neuroretinal epithelial cell fate specification

Abstract

Cell differentiation is directed by extracellular cues and intrinsic epigenetic modifications, which control chromatin organization and transcriptional activation. Central to this process is PRC2, which modulates the di‐ and trimethylation of lysine 27 on histone 3; however, little is known concerning the direction of PRC2 to specific loci. Here, we have investigated the physical interactome of EZH2, the enzymatic core of PRC2, during retinoic acid‐mediated differentiation of neuroepithelial, pluripotent NT2 cells and the dedifferentiation of neuroretinal epithelial ARPE19 cells in response to TGF‐β. We identified Smad3 as an EZH2 interactor in both contexts. Co‐occupation of the CDH1 promoter by Smad3 and EZH2 and the cooperative, functional nature of the interaction were established. We propose that the interaction between Smad3 and EZH2 targets the core polycomb assembly to defined regions of the genome to regulate transcriptional repression and forms a molecular switch that controls promoter access through epigenetic mechanisms leading to gene silencing.—Andrews, D., Oliviero, G., De Chiara, L., Watson, A., Rochford, E., Wynne, K., Kennedy, C., Clerkin, S., Doyle, B., Godson, C., Connell, P., O'Brien, C., Cagney, G., Crean, J. Unravelling the transcriptional responses of TGF‐β: Smad3 and EZH2 constitute a regulatory switch that controls neuroretinal epithelial cell fate specification. FASEB J. 33, 6667–6681 (2019). http://www.fasebj.org

Gene silencing by EZH2 suppresses TGF-β activity within the decidua to avert pregnancy-adverse wound healing at the maternal-fetal interface

“…Specifically, we note that in the early decidua, where EZH2 is antifibrotic, both TGF-b1 and its close relative activin are expressed at high levels (Maurya et al, 2013;Ni and Li, 2017;Shooner et al, 2005). In addition, TGF-b and activin in part signal through the transcription factor SMAD3, which has recently been shown to physically interact with EZH2 (Andrews et al, 2019;Oliviero et al, 2016). Thus, we speculate that concomitant SMAD3/ PRC2 activation may establish an anti-fibrotic state that allows certain TGF-b target genes to be selectively marked for transcriptional silencing.…”

A polycomb-independent role of EZH2 in TGFβ1-damaged epithelium triggers a fibrotic cascade with mesenchymal cells

“…All raw files were processed with MaxQuant 6 (version 1.5.5.1) using the integrated Andromeda Search engine 7 against a target/decoy version of the curated human Uniprot proteome without isoforms (downloaded in January of 2019) and the GPM cRAP sequences (commonly known protein contaminants). First search peptide tolerance was set to 20 ppm, main search peptide tolerance was set to 4.5 ppm.…”

“…TGFβ1 is a predominant effector in most, if not all, forms of fibrosis. Several studies have uncovered an intricate crosstalk between SMADs, the central player of TGFβ signalling, and a myriad of epigenetic regulators to fine-tune the transcriptional machinery 7,8 . PRC2 is a major epigenetic repressive regulator consisting of EZH2, SUZ12 and EED.…”

An EZH2‐dependent transcriptional complex promotes aberrant epithelial remodelling after injury

“…TGFβ1 is a predominant effector in most forms of fibrosis; it is secreted and tethered to the ECM by many different cell types, including epithelial and MCs (Kim et al , 2018 ). Previous studies have uncovered an intricate crosstalk between SMADs, the central player of TGFβ signalling and a myriad of epigenetic regulators that fine‐tune transcriptional machinery (Andrews et al , 2019 ; Lu et al , 2019 ). PRC2 is a major epigenetic repressive regulator consisting of EZH2, SUZ12 and EED.…”