Identification of a cis-Acting Element and a Novel trans-Acting Factor of the Glutamine Synthetase Gene in Liver Cells

Gaunitz, Frank; Weber, Simon; Scheja, Ludger; Gebhardt, Rolf

doi:10.1006/bbrc.2001.4967

Cited by 11 publications

(16 citation statements)

References 29 publications

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“…Pericentral GS expression was first described in 1983,4, 25 and GS continues to be the most extensively studied pericentral gene. Several elements controlling GS activity have been identified in tissue‐culture cells, including a single upstream enhancer centered 2.2 kilobases (kb) upstream of exon 1 and several regulatory regions within the first intron 26‐30. Previous studies indicated that the 3.2‐kb region upstream of the rat GS gene (−3,150 to +59) could confer pericentral expression of a linked reporter gene in Tg mice 31.…”

Section: Resultsmentioning

confidence: 99%

Pericentral activity of alpha-fetoprotein enhancer 3 and glutamine synthetase upstream enhancer in the adult liver are regulated by β-catenin in mice

Clinkenbeard¹,

Butler²,

Spear

2012

Hepatology

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We previously showed that mouse alpha-fetoprotein enhancer E3 activity is highly restricted to pericentral hepatocytes in the adult liver. Here, using transgenic mice, we show that the upstream enhancer of the rat glutamine synthetase gene is also active specifically in pericentral regions. Activity of both enhancers is lost in the absence of β-catenin, a key regulator of zonal gene expression in the adult liver. Both enhancers contain a single highly conserved TCF/LEF binding site that is required for responsiveness to β-catenin. We also show that endogenous AFP mRNA levels in the perinatal liver are lower when β-catenin is reduced. These data identify the first distinct zonally-active regulatory regions required for β-catenin responsiveness in the adult liver and suggest that postnatal AFP repression and the establishment of zonal regulation are controlled, at least in part, by the same factors.

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Section: Resultsmentioning

confidence: 99%

Pericentral activity of alpha-fetoprotein enhancer 3 and glutamine synthetase upstream enhancer in the adult liver are regulated by β-catenin in mice

Clinkenbeard¹,

Butler²,

Spear

2012

Hepatology

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“…At the level of transcription regulatory elements have been described in the first intron 15 and in 5Ј upstream regions. 7,8 New data also confirm that posttranscriptional events such as differential splicing may contribute to fine-tuning of expression by altering translation. 16 In the work presented, we focused on the GS 5Ј enhancer and proteins binding to this element.…”

Section: Discussionmentioning

confidence: 79%

“…In previous experiments, it was shown that this GS enhancer strongly binds a factor present in rat liver nuclear extracts. 8 However, the nature of this protein was unknown. Data base analysis at the time the experiments were initiated did not reveal any candidate factor.…”

Section: Purification Of Nuclear Proteins Binding To the 5-enhancer Ementioning

confidence: 99%

“…In fact, the 5Ј enhancer located Ϸ2520 base pairs (bp) 5Ј upstream from the transcriptional start point (tsp) appears to be the most potent element known to act as a positive regulator of GS expression. 7,8 In the present study, we identified transcription factors that bind to this enhancer through purification of nuclear proteins, footprint and binding assays, as well as supershift EMSA techniques. Functional assays using various reporter constructs and hormonal challenge of the transfected hepatocytes revealed a surprising interaction of transcription factors that may explain many details of the cross-talk between growth hormone/cytokine-dependent and wnt/␤-catenin-dependent signaling pathways, the two most important regulatory pathways of hepatic GS expression known to date.…”

mentioning

confidence: 99%

“…Primary nuclear extracts from ten rat livers were prepared as described. 8 Starting material for the following purification steps were 400 mg of nuclear protein suspended in Buffer A (10 mmol/L HEPES pH 7.6, 0.1 mol/L KCl, 1 mmol/L EDTA, 0.5 mol/L dithiothreitol, and 10% glycerol). The dialyzed nuclear extracts were applied to a 20 mL phosphocellulose column (Serva, Heidelberg, Germany), washed with buffer A, and proteins were eluted with increasing concentrations of KCl.…”

mentioning

confidence: 99%

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Hepatic expression of glutamine synthetase in rats is controlled by STAT5 and TCF transcription factors

2006

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In mammalian liver, high glutamine synthetase (GS) expression is restricted to hepatocytes surrounding the terminal venules. The most important enhancer of the GS gene is located Ϸ2520 base pairs (bp) upstream from the transcriptional start point. The nature of the transcription factors that bind to the enhancers has remained enigmatic. In this study, we purified nuclear proteins binding to the element. Supershift assays and footprint experiments with purified protein identified activated STAT5 as a transcription factor binding to a site within the enhancer.

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An intronic silencer element is responsible for specific zonal expression of glutamine synthetase in the rat liver

et al. 2005

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The most striking phenomenon of glutamine synthetase (GS) expression in the liver is its unique restriction to cells surrounding the terminal hepatic venules. Expression is positively regulated by elements located in the 5 -upstream region and in the first intron of the gene. It was long believed that transcription factors present in GS-positive cells and absent in GSnegative cells are responsible for the phenomenon of zonal expression. However, strong enhancers are equally active in both types of cells. Therefore, the existence of a silencer mechanism in GS-negative hepatocytes was postulated. In the present study, a GS silencer element was investigated that was previously identified within the first intron and was shown to be able to prevent glucocorticoid-induced expression in cells negative for a transacting factor designated GS silencer element-binding protein. Reporter gene assays with the silencer element in combination with the most potent 5 -enhancer of the GS gene demonstrate that the silencer element is able to prevent enhancement mediated by the 5 -enhancer in combination with a heterologous as well as with the homologous promoter. More importantly, the effect of the silencer is shown to be restricted to GS-negative hepatocytes. In conclusion, the phenomenon of zonal expression of GS in the liver is caused by a protein present in GS-negative cells and absent in GS-positive cells that interacts with the silencer element in the first intron and not by a differential expression of enhancer-binding proteins.

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Identification of a cis-Acting Element and a Novel trans-Acting Factor of the Glutamine Synthetase Gene in Liver Cells

Cited by 11 publications

References 29 publications

Pericentral activity of alpha-fetoprotein enhancer 3 and glutamine synthetase upstream enhancer in the adult liver are regulated by β-catenin in mice

Pericentral activity of alpha-fetoprotein enhancer 3 and glutamine synthetase upstream enhancer in the adult liver are regulated by β-catenin in mice

Hepatic expression of glutamine synthetase in rats is controlled by STAT5 and TCF transcription factors

An intronic silencer element is responsible for specific zonal expression of glutamine synthetase in the rat liver

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