| Summary: | 碩士 === 慈濟大學 === 醫學檢驗生物技術學系醫學生物技術碩士班 === 102 === Snail is high expression with cancer metastasis. Snail regulates many genes expression and participate epithelial mesenchymal transition (EMT). For inhibition of transcription machinery, Snail can bind on E-box of E-cadherin promoter and suppress E-cadherin expression. Reduction of E-cadherin expression makes cell adhesion friability. Snail can promote Matrix metalloproteinase expression. Matrix metalloproteinase degrade extracellular matrix and help cell movement and invasion. Snail can promote Zinc finger E-box-binding homeobox 1 (ZEB1) expression, which can change cytoskeleton and cell shape. Snail has been reported to suppress some genes expression. However, the transcription machinery for Snail to upregulate gene expression is not clear thus far. Our recent report demonstrated Snail associates with EGR-1 and SP-1 to upregulate transcription of p15INK4b induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in human hepatoma HepG2 cells. We found a novel sequence motif TCACA upstream of EGR-1/SP-1 overlapping region for Snail to bind on p15INK4b promoter. We further investigated transcriptional mechanism of matrix metalloproteinase 9 (MMP9), one of the matrix degradation enzyme and Zinc finger E-box-binding homeobox 1 (ZEB1), which are also upregulated by Snail. Using deletion mapping analysis, we identified TPA-responsive element of MMP-9 and ZEB1 promoter located between -950~-771 bp, and -1061~-967 bp, respectively, upstream of the transcriptional initiation site. Interestingly, these regions also contain proposed Snail-target motif close to EGR-1/SP-1 overlapping site. Moreover, site directed mutagenesis of proposed Snail-target motif on both MMP9 and ZEB1 full length promoter abolished TPA-induced promoter activity of both genes. On the other hand, ChIP assay demonstrated TPA induced binding of Snail to promoter fragment of both genes containing proposed Snail-target site. For double ChIP, it is confirmed Snail, Egr1 and Sp1 binding on ZEB1 promoter together. Our study will establish that Snail upregulate gene expression via binding to concensus promoter region close to EGR-1/SP-1 overlapping region.
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