Abstract
Epithelial-mesenchymal transition (EMT) is essential for organogenesis and is triggered during carcinoma progression to an invasive state. Transforming growth factor-beta (TGF-beta) cooperates with signalling pathways, such as Ras and Wnt, to induce EMT, but the molecular mechanisms are not clear. Here, we report that SMAD3 and SMAD4 interact and form a complex with SNAIL1, a transcriptional repressor and promoter of EMT. The SNAIL1-SMAD3/4 complex was targeted to the gene promoters of CAR, a tight-junction protein, and E-cadherin during TGF-beta-driven EMT in breast epithelial cells. SNAIL1 and SMAD3/4 acted as co-repressors of CAR, occludin, claudin-3 and E-cadherin promoters in transfected cells. Conversely, co-silencing of SNAIL1 and SMAD4 by siRNA inhibited repression of CAR and occludin during EMT. Moreover, loss of CAR and E-cadherin correlated with nuclear co-expression of SNAIL1 and SMAD3/4 in a mouse model of breast carcinoma and at the invasive fronts of human breast cancer. We propose that activation of a SNAIL1-SMAD3/4 transcriptional complex represents a mechanism of gene repression during EMT.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Blotting, Western
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Cadherins / genetics
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Cell Line, Transformed
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Cell Nucleus / metabolism
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Chromatin Immunoprecipitation
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Epithelial Cells / drug effects
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Epithelial Cells / metabolism
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Epithelial Cells / pathology
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Humans
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Intercellular Junctions / metabolism
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Mammary Neoplasms, Experimental / genetics
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Mammary Neoplasms, Experimental / metabolism
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Mammary Neoplasms, Experimental / pathology
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Mesoderm / drug effects
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Mesoderm / metabolism
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Mesoderm / pathology
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Mice
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Mice, Inbred BALB C
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Microscopy, Fluorescence
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Promoter Regions, Genetic / genetics
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Protein Binding
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Reverse Transcriptase Polymerase Chain Reaction
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Smad3 Protein / genetics
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Smad3 Protein / metabolism*
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Smad4 Protein / genetics
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Smad4 Protein / metabolism*
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Snail Family Transcription Factors
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transforming Growth Factor beta / pharmacology*
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Tumor Cells, Cultured
Substances
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Cadherins
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SMAD4 protein, human
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SNAI1 protein, human
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Smad3 Protein
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Smad3 protein, mouse
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Smad4 Protein
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Snai1 protein, mouse
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Snail Family Transcription Factors
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Transcription Factors
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Transforming Growth Factor beta