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Inhibitory effect of TIS7 on Sp1-C/EBPalpha transcription factor module activity
N Wick1, A Schleiffer, L A Huber
1Clinical Institute for Pathology, University of Vienna, Austria Waehringer Guertel 18-20, A-1190 Vienna, Austria.
Abstract:
The transcription factors C/EBPalpha and Sp1 functionally interact to induce expression of specific genes during myeloid and epithelial cell differentiation. The C/EBPalpha-Sp1 transcription factor "module" binds to enhancer elements within the upstream regulatory sequences of target genes. In our previous study we identified mouse TPA inducible sequence 7 (TIS7) as a novel co-repressor in epithelial cells undergoing loss of polarity. Increased levels of TIS7 down-regulate the transcription of a specific set of genes. Using bioinformatic analysis we identified a common binding site for the C/EBPalpha-Spl transcription factor module within the upstream regulatory regions of TIS7-regulated genes. The inhibitory effect of TIS7 on C/EBPalpha-Sp1-mediated transcription was confirmed by reporter assays. Our data showed that the TIS7 effect was mediated through specific interference with Sp1 transcriptional activity. Furthermore, TIS7 prevented formation of a complex between Sp1 protein and its consensus DNA binding site. Data presented here further specify the mechanism of action of the transcriptional co-repressor TIS7 as well as document the strength of a bioinformatic approach for the prediction and analysis of transcription factor modules.
Insights
Transcriptional co-repressor TIS7 inhibits gene expression by interfering with the C/EBPalpha-Sp1 transcription factor module. This study details TIS7
Area of Science:
- Molecular Biology
- Gene Regulation
- Transcription Factors
Background:
- C/EBPalpha and Sp1 transcription factors form a module that drives gene expression during cell differentiation.
- TIS7 (TPA inducible sequence 7) acts as a co-repressor, down-regulating specific gene transcription in epithelial cells.
- Previous work identified TIS7 as a co-repressor in epithelial cells experiencing loss of polarity.
Purpose of the Study:
- To investigate the mechanism by which TIS7 inhibits gene transcription.
- To determine if TIS7 interacts with the C/EBPalpha-Sp1 transcription factor module.
- To validate the utility of bioinformatic analysis in predicting transcription factor module interactions.
Main Methods:
- Bioinformatic analysis to identify common binding sites for the C/EBPalpha-Sp1 module in TIS7-regulated genes.
- Reporter assays to confirm the inhibitory effect of TIS7 on C/EBPalpha-Sp1-mediated transcription.
- Experiments to elucidate the specific interference of TIS7 with Sp1 transcriptional activity and DNA binding.
Main Results:
- A common binding site for the C/EBPalpha-Sp1 module was identified in the regulatory regions of TIS7-regulated genes.
- TIS7 was confirmed to inhibit C/EBPalpha-Sp1-mediated transcription.
- TIS7 was shown to interfere with Sp1 transcriptional activity and prevent Sp1 binding to its consensus DNA site.
Conclusions:
- TIS7 functions as a transcriptional co-repressor by specifically interfering with Sp1 activity within the C/EBPalpha-Sp1 module.
- This interference prevents the formation of a functional Sp1-DNA complex, thereby down-regulating target gene expression.
- The study highlights the effectiveness of bioinformatic approaches for predicting and analyzing transcription factor module functions.
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