SIP1/ZEB2 induces EMT by repressing genes of different epithelial cell–cell junctions

SIP1/ZEB2 is a member of the δEF-1 family of two-handed zinc finger nuclear factors. The expression of these transcription factors is associated with epithelial mesenchymal transitions (EMT) during development. SIP1 is also expressed in some breast cancer cell lines and was detected in intestinal gastric carcinomas, where its expression is inversely correlated with that of E-cadherin. Here, we show that expression of SIP1 in human epithelial cells results in a clear morphological change from an epithelial to a mesenchymal phenotype. Induction of this epithelial dedifferentiation was accompanied by repression of several cell junctional proteins, with concomitant repression of their mRNA levels. Besides E-cadherin, other genes coding for crucial proteins of tight junctions, desmosomes and gap junctions were found to be transcriptionally regulated by the transcriptional repressor SIP1. Moreover, study of the promoter regions of selected genes by luciferase reporter assays and chromatin immunoprecipitation shows that repression is directly mediated by SIP1. These data indicate that, during epithelial dedifferentiation, SIP1 represses in a coordinated manner the transcription of genes coding for junctional proteins contributing to the dedifferentiated state; this repression occurs by a general mechanism mediated by Smad Interacting Protein 1 (SIP1)-binding sites

Behavior of the different proteins of the cadherin–catenin complex upon SIP1 induction

<p><b>Copyright information:</b></p><p>Taken from "SIP1/ZEB2 induces EMT by repressing genes of different epithelial cell–cell junctions"</p><p>Nucleic Acids Research 2005;33(20):6566-6578.</p><p>Published online 24 Nov 2005</p><p>PMCID:PMC1298926.</p><p>© The Author 2005. Published by Oxford University Press. All rights reserved</p> () Immunofluorescence microscopy of non-induced and induced DLD1Tr21/WTSIP1 cells using antibodies specific for adherens junction components. E-cadherin as well as αE-catenin, p120ctn and β-catenin became nearly undetectable at cell–cell contacts in the SIP1-induced cells. () Western blot analysis of the non-induced and induced DLD1Tr21/WTSIP1 cell line. E-cadherin and αE-catenin were downregulated at the protein level in the SIP1-expressing cells. β-catenin protein levels were unaltered in the SIP1-induced compared to non-induced cells. Protein expression of p120ctn isoform 1 was upregulated and that of isoform 3 downregulated after SIP1 induction (: addition of Dox every 2 days, : washing away Dox from the cell culture medium)