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Transcriptional repression, a novel function for 3' untranslated regions
1INSERM, Montpellier, France.
European Journal of Biochemistry
|August 1, 1995
Summary
A specific 3' untranslated region (UTR) extension in the rat serine protease inhibitor 2.3 (spi 2.3) gene acts as a silencer, reducing transcription. This UTR element explains low basal transcription and inflammation-induced gene expression.
Area of Science:
- Molecular Biology
- Gene Regulation
- Biochemistry
Background:
- Rat serine protease inhibitor 2.1 (spi 2.1) and 2.3 (spi 2.3) genes exhibit inversely modulated transcription rates during inflammation.
- The spi 2.1 gene is tightly regulated by growth hormone via specific response elements (GHRE-I and GHRE-II).
- The spi 2.3 gene appears to evade growth hormone control despite possessing a functional GHRE-I element.
Purpose of the Study:
- To investigate the role of a unique 348-bp 3' untranslated region (UTR) extension in the spi 2.3 gene.
- To elucidate the mechanism by which this 3' UTR extension influences gene transcription.
- To determine the impact of this element on the regulation of both spi 2.3 and spi 2.1 gene expression.
Main Methods:
- Construction of reporter gene assays using chloramphenicol acetyltransferase (CAT) with the spi 2.3 3' UTR element inserted at different positions.
- Analysis of basal and stimulated transcription rates in response to growth hormone, dexamethasone, and interleukin-6.
- Site-directed mutagenesis of key promoter elements, including the GAGA box and CCAAT enhancer-binding-protein (C/EBP)-binding sites.
Main Results:
- The spi 2.3 3' UTR extension significantly decreased basal transcription and inhibited growth hormone-stimulated transcription.
- This UTR element showed minimal effect on transcription stimulated by dexamethasone or interleukin-6.
- The 3' UTR extension also inhibited basal and growth hormone-induced transcription from the spi 2.1 promoter, indicating a broader repressive function.
Conclusions:
- The 3' UTR extension of the spi 2.3 gene functions as a potent silencer, affecting both spi 2.3 and spi 2.1 gene transcription.
- Repressor activity involves interactions with promoter elements, specifically the GAGA box and C/EBP-binding sites.
- This silencer element likely explains the low basal transcription of spi 2.3 in vivo and its induction during inflammation.