1
40
5
-
Text
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URL Address
<a href="http://doi.org/10.1016/s0378-1119(00)00518-7" target="_blank" rel="noreferrer noopener">http://doi.org/10.1016/s0378-1119(00)00518-7</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
257-265
Issue
1
Volume
262
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Dublin Core
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Title
A name given to the resource
Regulation of cholesterol 7 alpha-hydroxylase gene (CYP7A1) transcription by the liver orphan receptor (LXR alpha)
Publisher
An entity responsible for making the resource available
Gene
Date
A point or period of time associated with an event in the lifecycle of the resource
2001
2001-01
Subject
The topic of the resource
bile acid synthesis; expression; Signaling; dietary-cholesterol; Bile acids; pathway; nuclear receptor; nuclear receptors; promoter; Genetics & Heredity; x-receptor; cytochrome P450; gene regulation; reverse cholesterol transport; hepg2 cells; coup-tfii; ligands
Creator
An entity primarily responsible for making the resource
Chiang J Y L; Kimmel R; Stroup D
Description
An account of the resource
The cholesterol 7 alpha -hydroxylase gene (CYP7A1) plays an important role in regulation of bile acid biosynthesis and cholesterol homeostasis. Oxysterol receptor, LXR, stimulates, whereas the bile acid receptor, FXR, inhibits CYP7A1 transcription. The goal of this study was to investigate the role of LXR alpha on the regulation of rat, human and hamster CYP7A1 transcription in its native promoter and cellular context. Cotransfection with LXR alpha and RXR alpha expression plasmids strongly stimulated rat CYP7A1/luciferase reporter activity in HepG2 cells and oxysterol was not required. However, LXR alpha had much less effect on hamster and no significant effect on human CYP7A1 promoter activity in HepG2 cells. In Chinese hamster ovary cells, cotransfection with LXR alpha stimulated reporter activity by less than 2-fold and addition of 22(R)-hydroxycholesterol caused a small but significant stimulation of rat, human and hamster CYP7A1 promoter activity. At least two direct repeats of AGGTCA-like sequences with 4-base spacing (DR4) and five-base spacing (DR5), in previously identified bile acid response elements of the rat CYP7A1 were able to bind LXR alpha /RXR alpha and confer LXR alpha stimulation. However, LXR alpha did not bind to the corresponding sequences of the human gene and bound weakly to hamster and mouse DR4 sequences. Therefore, rats and mice have the unusual capacity to convert cholesterol to bile acids by LXR alpha -mediated stimulation of CYP7A1 transcription, whereas other species do not respond to cholesterol and develop hypercholesterolemia on a diet high in cholesterol. (C) 2001 Elsevier Science B.V. All rights reserved.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1016/s0378-1119(00)00518-7" target="_blank" rel="noreferrer noopener">10.1016/s0378-1119(00)00518-7</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article or Conference Abstract Publication
2001
Bile acid synthesis
BILE acids
Chiang J Y L
coup-tfii
cytochrome P450
dietary-cholesterol
expression
gene
Gene Regulation
Genetics & Heredity
hepg2 cells
Journal Article or Conference Abstract Publication
Kimmel R
Ligands
Nuclear Receptor
Nuclear Receptors
pathway
promoter
reverse cholesterol transport
Signaling
Stroup D
x-receptor
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1111/j.1432-1033.1993.tb18082.x" target="_blank" rel="noreferrer noopener">http://doi.org/10.1111/j.1432-1033.1993.tb18082.x</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
705-710
Issue
3
Volume
215
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Dublin Core
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Title
A name given to the resource
CHOLESTEROL 7-ALPHA-HYDROXYLASE IS UP-REGULATED BY THE COMPETITIVE INHIBITOR 7-OXOCHOLESTEROL IN RAT-LIVER
Publisher
An entity responsible for making the resource available
European Journal of Biochemistry
Date
A point or period of time associated with an event in the lifecycle of the resource
1993
1993-08
Subject
The topic of the resource
Biochemistry & Molecular Biology; expression; cloning; dietary-cholesterol; purification; messenger-rna; circadian-rhythm; reductase; microsomes; sequence; serum-cholesterol
Creator
An entity primarily responsible for making the resource
Breuer O; Sudjanasugiaman E; Eggertsen G; Chiang J Y L; Bjorkhem I
Description
An account of the resource
Rats of the Sprague-Dawley strain were infused intravenously with a fat emulsion (Intralipid, trademark of Kabi Pharmacia, Uppsala, Sweden) containing 7-oxocholesterol. This resulted in an increased cholesterol 7alpha-hydroxylase activity in liver microsomes as compared to controls and was accompanied by increased levels of cholesterol 7alpha-hydroxylase mRNA and microsomal cholesterol 7alpha-hydroxylase protein. Rats were also fed a cholestyramine-supplemented diet and infused with 7-oxocholesterol. These animals excreted about half as much bile acids in faeces as cholestyramine-fed controls. Addition of 7-oxocholesterol to liver microsomes from normal rats in amounts corresponding to those present in microsomes from 7-oxocholesterol-treated rats inhibited the cholesterol 7alpha-hydroxylase activity by about 75%. Cholesterol induced a type-I binding spectrum when added to a purified bacterial-expressed cholesterol 7alpha-hydroxylase (P-450c7DELTA2-24). 7-Oxocholesterol competitively inhibited the cholesterol binding spectrum, while 7beta-hydroxycholesterol did not interfere with binding of cholesterol to the enzyme. It is concluded that treatment with the competitive inhibitor 7-oxocholesterol leads to a reduced bile acid biosynthesis and, as a consequence of reduced bile acid inhibition, a compensatory increase in cholesterol 7alpha-hydroxylase synthesis. The high enzyme activity measured in microsomal preparations from 7-oxocholesterol-treated rats may be due to a continuous conversion of 7-oxocholesterol into less inhibitory metabolites, e.g. 7beta-hydroxycholesterol. The latter compound was found in high concentrations in liver microsomes from rats treated with 7-oxocholesterol. The physiological importance of these results is discussed in relation to the previous findings that 7-oxocholesterol is accumulated in liver after cholesterol feeding and that 7-oxocholesterol is formed from cholesterol during lipid peroxidation.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1111/j.1432-1033.1993.tb18082.x" target="_blank" rel="noreferrer noopener">10.1111/j.1432-1033.1993.tb18082.x</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article or Conference Abstract Publication
1993
Biochemistry & Molecular Biology
Bjorkhem I
Breuer O
Chiang J Y L
circadian-rhythm
Cloning
dietary-cholesterol
Eggertsen G
European Journal of Biochemistry
expression
Journal Article or Conference Abstract Publication
messenger-rna
Microsomes
purification
reductase
sequence
serum-cholesterol
Sudjanasugiaman E
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1194/jlr.M500449-JLR200" target="_blank" rel="noreferrer noopener">http://doi.org/10.1194/jlr.M500449-JLR200</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
997-1004
Issue
5
Volume
47
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Title
A name given to the resource
The stimulatory effect of LXR alpha is blocked by SHP despite the presence of a LXR alpha binding site in the rabbit CYP7A1 promoter
Publisher
An entity responsible for making the resource available
Journal of Lipid Research
Date
A point or period of time associated with an event in the lifecycle of the resource
2006
2006-05
Subject
The topic of the resource
alpha-fetoprotein transcription; bile-acid biosynthesis; Biochemistry & Molecular Biology; cholesterol 7 alpha-hydroxylase; cholesterol 7-alpha-hydroxylase gene; dietary-cholesterol; dietary-cholesterol; factor; farnesoid X receptor; farnesoid X receptor; inhibition; liver X receptor; messenger-rna levels; nuclear receptor; orphan; rat; SHP; taurocholate; transcription
Creator
An entity primarily responsible for making the resource
Shang Q; Pan L X; Saumoy M; Chiang J Y L; Tint G S; Salen G; Xu G R
Description
An account of the resource
The transcription of the cholesterol 7 alpha-hydroxylase gene (CYP7A1) is greatly decreased in cholesterol-fed rabbits. To determine whether the molecular structure of the promoter is responsible for this downregulation, we cloned the rabbit CYP7A1 promoter, identified the binding sites for a-fetoprotein transcription factor (FTF) and liver X receptor (LXR alpha), and studied the effects of FTF, LXR alpha, and SHP on its transcription. Adding LXR alpha/retinoid X receptor together with their ligands (L/R) to the promoter/reporter construct transfected into HepG2 cells greatly increased its activity. FTF did not increase promoter activity, nor did it enhance the stimulatory effect of L/R. Mutating the FTF binding site abolished the promoter baseline activity. Increasing amounts of SHP abolished the effect of L/R, and FTF enhanced the ability of SHP to decrease promoter activity below baseline levels. Thus, downregulation of CYP7A1 in cholesterol-fed rabbits is attributable secondarily to the activation of farnesoid X receptor, which increases SHP expression to override the positive effects of LXR alpha. Although FFF is a competent factor for maintaining baseline activity, it does not further enhance and may suppress CYP7A1 transcription.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1194/jlr.M500449-JLR200" target="_blank" rel="noreferrer noopener">10.1194/jlr.M500449-JLR200</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
2006
alpha-fetoprotein transcription
bile-acid biosynthesis
Biochemistry & Molecular Biology
Chiang J Y L
cholesterol 7 alpha-hydroxylase
cholesterol 7-alpha-hydroxylase gene
dietary-cholesterol
factor
Farnesoid X receptor
inhibition
Journal Article
Journal of lipid research
liver X receptor
messenger-rna levels
Nuclear Receptor
orphan
Pan L X
rat
Salen G
Saumoy M
Shang Q
SHP
taurocholate
Tint G S
Transcription
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1152/ajpgi.00209.2007" target="_blank" rel="noreferrer noopener">http://doi.org/10.1152/ajpgi.00209.2007</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
G817-G823
Issue
4
Volume
293
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Dublin Core
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Title
A name given to the resource
An overlapping binding site in the CYP7A1 promoter allows activation of FXR to override the stimulation by LXR alpha
Publisher
An entity responsible for making the resource available
American Journal of Physiology-Gastrointestinal and Liver Physiology
Date
A point or period of time associated with an event in the lifecycle of the resource
2007
2007-10
Subject
The topic of the resource
7-alpha-hydroxylase gene; activity; bile-acid biosynthesis; cholesterol; cholesterol 7 alpha-hydroxylase; dietary-cholesterol; down-regulation; farnesoid X; fetoprotein transcription factor; Gastroenterology & Hepatology; heterodimer partner; liver X receptor; LXR binding site; messenger-rna; metabolism; orphan nuclear receptor; Physiology; rat; receptor; regulation; short; transcriptional; x-receptor
Creator
An entity primarily responsible for making the resource
Shang Q; Pan L X; Saumoy M; Chiang J Y L; Tint G S; Salen G; Xu G R
Description
An account of the resource
An overlapping binding site in the CYP7A1 promoter allows activation of FXR to override the stimulation by LXR alpha. Am J Physiol Gastrointest Liver Physiol 293: G817-G823, 2007. First published August 9, 2007; doi:10.1152/ajpgi.00209.2007.-The aim of this study was to explore why in rabbits activation of farnesoid X receptor (FXR) is dominant over activated liver X receptor-alpha (LXR alpha) in the regulation of CYP7A1. We cloned the rabbit CYP7A1 promoter and found a fetoprotein transcription factor (FTF) binding element embedded within the LXR alpha binding site (LXRE). Gel shift assays demonstrated that FTF competes with LXR alpha for binding to LXRE. Short heterodimer partner (SHP) enhances the competitive ability of FTF. Studies in HepG2 cells showed that SHP combined with FTF had more powerful effect to offset the stimulation of CYP7A1 by LXR alpha. Gel shift and chromatin immunoprecipitation assays demonstrated that SHP with FTF diminished LXR alpha\binding to the CYP7A1 promoter. In vivo studies in rabbits fed cholesterol for 10 days showed that hepatic expression of SHP but not FTF rose and LXR alpha-bound LXRE decreased. We propose that the SHP/FTF heterodimer occupies LXRE via the embedded FTF binding element and blocks LXR alpha from recruiting to LXRE. Therefore, activation of FXR, which upregulates SHP expression, will eliminate the stimulatory effect of LXR alpha on the CYP7A1 promoter because increased levels of SHP combined with FTF diminish the recruitment of LXR alpha to CYP7A1 promoter.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1152/ajpgi.00209.2007" target="_blank" rel="noreferrer noopener">10.1152/ajpgi.00209.2007</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
2007
7-alpha-hydroxylase gene
activity
American Journal of Physiology-Gastrointestinal and Liver Physiology
bile-acid biosynthesis
Chiang J Y L
Cholesterol
cholesterol 7 alpha-hydroxylase
dietary-cholesterol
Down-Regulation
farnesoid X
fetoprotein transcription factor
Gastroenterology & Hepatology
heterodimer partner
Journal Article
liver X receptor
LXR binding site
messenger-rna
Metabolism
orphan nuclear receptor
Pan L X
Physiology
rat
Receptor
regulation
Salen G
Saumoy M
Shang Q
short
Tint G S
transcriptional
x-receptor
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1053/jhep.1996.v24.pm0008938182" target="_blank" rel="noreferrer noopener">http://doi.org/10.1053/jhep.1996.v24.pm0008938182</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
1468-1474
Issue
6
Volume
24
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Cholesterol 7 alpha-hydroxylase activities from human and rat liver are modulated in vitro posttranslationally by phosphorylation/dephosphorylation
Publisher
An entity responsible for making the resource available
Hepatology
Date
A point or period of time associated with an event in the lifecycle of the resource
1996
1996-12
Subject
The topic of the resource
bile-acid synthesis; cloning; dietary-cholesterol; enzyme; Escherichia coli; expression; Gastroenterology & Hepatology; hmg-coa reductase; messenger-rna levels; Phosphatase; purification
Creator
An entity primarily responsible for making the resource
Nguyen L B; Shefer S; Salen G; Chiang J Y L; Patel M
Description
An account of the resource
Purified cholesterol 7 alpha-hydroxylases (C7 alpha H) from human and rat liver microsomes, and from transformed Escherichia coli expression systems, were incubated with 0.3 mmol/L [gamma-P-32] adenosine triphosphate (ATP) in the presence and absence of bacterial alkaline phosphatase (AP) or rabbit muscle adenosine 3',5'-cyclic monophosphate (cAMP) dependent protein kinase. The amounts of P-32 incorporation after separation of human and rat C7 alpha H proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were related to C7 alpha H catalytic activities (determined by a radioisotope incorporation method) and enzyme protein mass (determined by Western blotting and laser densitometry). Both human and rat C7 alpha H activities significantly decreased after dephosphorylation by AP (-57%--72%) and increased up to twofold with phosphorylation by rabbit muscle cAMP-dependent protein kinase. The increases in C7 alpha H activities were proportional to the amounts of cAMP-dependent protein kinase used, and were coupled to P-32 incorporation into the purified enzymes, Both the activation of C7 alpha H and the amounts of P-32 incorporation were time-dependent and reached a maximum after 1 hour of incubation with 5 U of cAMP-dependent protein kinase. In a second set of experiments, purified human and rat Liver C7 alpha H were dephosphorylated by 30-minute incubation with AP, followed by inactivation of the phosphatase by the inhibitor NaF, and rephosphorylation of C7 alpha H by 30-minute incubation with rabbit muscle cAMP-dependent protein kinase or bovine heart cAMP-independent protein kinase. Rephosphorylation of the dephosphorylated C7 alpha H proteins by cAMP-dependent protein kinase increased C7 alpha H catalytic activities up to fourfold, and the stimulation in catalytic activities paralleled the increases in P-32 incorporation into the purified enzymes. Bovine heart protein kinase was as potent as rabbit muscle cAMP-dependent protein kinase in stimulating catalytic activity and P-32 incorporation into the human C7 alpha H protein. Because the protein mass of these purified enzymes did not change, the short-term regulation or catalytic efficiency of C7 alpha H (activity per protein mass unit) is modulated, in vitro, posttranslationally by a phosphorylation/ dephosphorylation mechanism in both the human and the rat enzymes.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1053/jhep.1996.v24.pm0008938182" target="_blank" rel="noreferrer noopener">10.1053/jhep.1996.v24.pm0008938182</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
1996
bile-acid synthesis
Chiang J Y L
Cloning
Department of Internal Medicine
dietary-cholesterol
enzyme
Escherichia coli
expression
Gastroenterology & Hepatology
Hepatology
HMG-CoA reductase
Journal Article
messenger-rna levels
NEOMED College of Medicine
Nguyen L B
Patel M
Phosphatase
purification
Salen G
Shefer S