| 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 === 100 === The Snail families of zinc-finger transcription factors may trigger epithelial mesenchymal transition (EMT) required for embryonic development and tumor metastasis. A lot of genes were known to be either positively or negatively regulated by Snail. As a transcriptional repressor, Snail may bind to consensus sequence E-box, thus interfering gene expression of epithelial markers such as E-cadherin.
However, how Snail 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 which is also upregulated by Snail. Using deletion mapping analysis, we identify TPA-responsive element of MMP-9 promoter located between -950~-771 bp upstream of the transcriptional initiation site. Interestingly, this region also contain proposed Snail-target site upstream of EGR-1/SP-1 overlapping region. TPA –induced MMP9 promoter activity abolished if the binding regions of Snail and EGR-1/SP-1 were mutated.
Also, ChIP assay further demonstrated TPA induced binding of Snail, EGR-1and SP-1 to their respective promoter region. Currently, we also investigate transcriptional mechanisms of other TPA-inducible, Snail-upregulated genes including ZEB-1. The preliminary results demonstrated TPA-responsive elements within promoters of these genes also contain proposed Snail-target site upstream of EGR-1/SP-1 overlapping region.
Collectively, our result highlighted that Snail cooperate with EGR-1/SP-1 to upregulate gene expression via binding to concensus promoter region.
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