scholarly journals Synergism between nuclear receptors bound to specific hormone response elements of the hepatic control region-1 and the proximal apolipoprotein C-II promoter mediate apolipoprotein C-II gene regulation by bile acids and retinoids

2003 ◽  
Vol 372 (2) ◽  
pp. 291-304 ◽  
Author(s):  
Dimitris KARDASSIS ◽  
Anastasia ROUSSOU ◽  
Paraskevi PAPAKOSTA ◽  
Konstantinos BOULIAS ◽  
Iannis TALIANIDIS ◽  
...  
Keyword(s):  
Bile Acids ◽  
Nuclear Receptors ◽  
Control Region ◽  
Hepg2 Cells ◽  
Mrna Levels ◽  
Hormone Response ◽  
Response Elements ◽  
Hormone Response Elements ◽  
Apolipoprotein C ◽  
Promoter Cluster

We have shown previously that the hepatic control region 1 (HCR-1) enhances the activity of the human apolipoprotein C-II (apoC-II) promoter in HepG2 cells via two hormone response elements (HREs) present in the apoC-II promoter. In the present paper, we report that the HCR-1 selectively mediates the transactivation of the apoC-II promoter by chenodeoxycholic acid (CDCA) and 9-cis-retinoic acid. CDCA, which is a natural ligand of farnesoid X receptor α (FXRα), increases the steady-state apoC-II mRNA levels in HepG2 cells. This increase in transcription requires the binding of retinoid X receptor α (RXRα)–FXRα heterodimers to a novel inverted repeat with one nucleotide spacing (IR-1) present in the HCR-1. This element also binds hepatocyte nuclear factor 4 and apoA-I regulatory protein-1. Transactivation of the HCR-1/apoC-II promoter cluster by RXRα–FXRα heterodimers in the presence of CDCA was abolished by mutations either in the IR-1 HRE of the HCR-1 or in the thyroid HRE of the proximal apoC-II promoter, which binds RXRα–thyroid hormone receptor β (T3Rβ) heterodimers. The same mutations also abolished transactivation of the HCR-1/apoC-II promoter cluster by RXRα–T3Rβ heterodimers in the presence of tri-iodothyronine. The findings establish synergism between nuclear receptors bound to specific HREs of the proximal apoC-II promoter and the HCR-1, and suggest that this synergism mediates the induction of the HCR-1/apoC-II promoter cluster by bile acids and retinoids.

Regulation of regional expression in rat brain PC2 by thyroid hormone/characterization of novel negative thyroid hormone response elements in the PC2 promoter

2005 ◽  
Vol 288 (1) ◽  
pp. E236-E245 ◽  
Author(s):  
Xiaoxiong Shen ◽  
Qiao-Ling Li ◽  
Gregory A. Brent ◽  
Theodore C. Friedman
Keyword(s):  
Retinoic Acid ◽  
Thyroid Hormone ◽  
Thyroid Hormone Receptor ◽  
Specific Binding ◽  
Gh3 Cells ◽  
Mrna Levels ◽  
Hormone Response ◽  
Thyroid Status ◽  
Response Elements ◽  
Hormone Response Elements

The prohormone convertases (PCs) PC1 and PC2 are involved in the tissue-specific endoproteolytic processing of neuropeptide precursors within the secretory pathway. We previously showed that changes in thyroid status altered pituitary PC2 mRNA and that this regulation was due to triiodothyronine-dependent interaction of the thyroid hormone receptor (TR) with negative thyroid hormone response elements (nTREs) contained in a large proximal region of the human PC2 promoter. In the current study, we examined the in vivo regulation of brain PC2 mRNA by thyroid status and found that 6- n-propyl-2-thiouracil-induced hypothyroidism stimulated, whereas thyroxine-induced hyperthyroidism suppressed, PC2 mRNA levels in the rat hypothalamus and cerebral cortex. To address the mechanism of T3 regulation of the PC2 gene, we used human PC2 (hPC2) promoter constructs transiently transfected into GH3 cells and found that triiodothyronine negatively and 9- cis-retinoic acid positively regulated hPC2 promoter activity. EMSAs, using purified TRα1 and retinoid X receptor-β (RXRβ) proteins demonstrated that TRα bound the distal putative nTRE-containing oligonucleotide in the PC2 promoter, and RXR bound to both nTRE-containing oligonucleotides. EMSAs with oligonucleotides containing deletion mutations of the nTREs demonstrated that the binding to TR and RXR separately is reduced, but specific binding to TR and RXR together persists even with deletion of each putative nTRE. We conclude that there are two novel TRE-like sequences in the hPC2 promoter and that these regions act in concert in a unique manner to facilitate the effects of thyroid hormone and 9- cis-retinoic acid on PC2.

scholarly journals Thyroid hormone regulation of prohormone convertase 1 (PC1): regional expression in rat brain and in vitro characterization of negative thyroid hormone response elements

2004 ◽  
Vol 33 (1) ◽  
pp. 21-33 ◽  
Author(s):  
X Shen ◽  
QL Li ◽  
GA Brent ◽  
TC Friedman
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Specific Binding ◽  
Gh3 Cells ◽  
Mrna Levels ◽  
Hormone Response ◽  
Mobility Shift ◽  
Response Elements ◽  
Hormone Response Elements

Most pro-neuropeptides are processed by the prohormone convertases, PC1 and PC2. We previously reported that changes in thyroid status altered anterior pituitary PC1 mRNA and this regulation was due to triiodothyronine (T(3))-dependent interaction of thyroid hormone receptor (TR) with negative thyroid hormone response elements (nTREs) contained in a large region of the human PC1 promoter. In this study, we demonstrated that hypothyroidism stimulated, while hyperthyroidism suppressed, PC1 mRNA levels in rat hypothalamus and cerebral cortex, but not in hippocampus. In situ hybridization was used to confirm real-time PCR changes and localize the regulation within the hypothalamus and cortex. Using a human PC1 (hPC1) promoter construct (with and without deletions in two regions that each contain a negative TRE) transiently transfected into GH3 cells, we found that T(3) negatively regulated hPC1 promoter activity, and this regulation required both of these two regions. Electrophoretic mobility shift assays (EMSAs) using purified thyroid hormone receptor alpha1 (TRalpha1) and retinoid X receptor beta (RXRbeta) proteins demonstrated that RXR and TRalpha both bound the PC1 promoter. Addition of TRalpha1/RXRbeta to the wild-type PC1 probe demonstrated binding as both homodimers and a heterodimer. EMSAs with oligonucleotides containing deletion mutations of the putative nTREs demonstrated that the proximal nTRE binds more strongly to TR and RXR than the distal nTRE, but that both regions exhibit specific binding. We conclude that there are multiple novel TRE-like sequences in the hPC1 promoter and that these regions act in a unique manner to facilitate the negative effect of thyroid hormone on PC1.

scholarly journals Interactions between the Prohormone Convertase 2 Promoter and the Thyroid Hormone Receptor*

Endocrinology ◽  
2000 ◽  
Vol 141 (9) ◽  
pp. 3256-3266 ◽  
Author(s):  
Qiao-Ling Li ◽  
Erik Jansen ◽  
Gregory A. Brent ◽  
Syed Naqvi ◽  
John F. Wilber ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Hormone Receptor ◽  
Thyroid Hormone Receptor ◽  
Retinoid X Receptor ◽  
Gh3 Cells ◽  
Transcriptional Level ◽  
Mrna Levels ◽  
Hormone Response ◽  
Response Elements ◽  
Hormone Response Elements

Abstract The majority of prohormones are cleaved at paired basic residues to generate bioactive hormones by prohormone convertases (PCs). As PC1 and PC2, two neuroendocrine-specific PCs, appear to be the key enzymes capable of processing a variety of prohormones, alterations of PC2 and/or PC1 levels will probably have a profound effect on hormonal homeostasis. We investigated the regulation of PC2 messenger RNA (mRNA) by thyroid hormone using GH3 cells to demonstrate that T3 negatively regulated PC2 mRNA levels in a dose- and time-dependent fashion. Functional analysis of progressive 5′-deletions of the human (h) PC2 promoter luciferase constructs in GH3 cells demonstrated that the regulation probably occurs at the transcriptional level, and that putative negative thyroid hormone response elements were located within the region from −44 to +137 bp relative to the transcriptional start site. Transient transfections in JEG-3 cells and COS-1 cells showed that the suppressive effect of T3 was equally mediated by the thyroid hormone receptor (TR) isoforms TRα1 and TRβ1. Electrophoretic mobility shift assays using purified TRα1 and retinoid X receptor-β protein as well as GH3 nuclear extracts showed that regions from +51 to +71 bp and from +118 to +137 bp of the hPC2 promoter bind to TRα1 as both a monomer and a homodimer and with TRα1/retinoid X receptor-β as a heterodimer. Finally, the in vivo regulation of pituitary PC2 mRNA by thyroid status was demonstrated in rats. These results demonstrate that T3 negatively regulates PC2 expression at the transcriptional level and that functional negative thyroid hormone response elements exist in the hPC2 promoter. We postulate that the alterations of PC2 activity may mediate some of the pathophysiological consequences of hypo- or hyperthyroidism.

Identification of novel steroid target genes through the combination of bioinformatics and functional analysis of hormone response elements

2006 ◽  
Vol 339 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Kuniko Horie-Inoue ◽  
Kenichi Takayama ◽  
Hidemasa U. Bono ◽  
Yasuyoshi Ouchi ◽  
Yasushi Okazaki ◽  
...  
Keyword(s):  
Functional Analysis ◽  
Target Genes ◽  
Hormone Response ◽  
Response Elements ◽  
Hormone Response Elements

scholarly journals Cell Type-Specific Replication of Simian Virus 40 Conferred by Hormone Response Elements in the Late Promoter

2002 ◽  
Vol 76 (13) ◽  
pp. 6762-6770 ◽  
Author(s):  
Michael L. Farrell ◽  
Janet E. Mertz
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
Genome Replication ◽  
Hormone Response ◽  
Cell Type ◽  
Late Promoter ◽  
African Green Monkey Kidney ◽  
Response Elements ◽  
Hormone Response Elements ◽  
Cell Type Specific

ABSTRACT The late genes of SV40 are not expressed at significant levels until after the onset of viral DNA replication. We previously identified two hormone response elements (HREs) in the late promoter that contribute to this delay. Mutants defective in these HREs overexpress late RNA at early, but not late, times after transfection of CV-1PD cells. Overexpression of nuclear receptors (NRs) that recognize these HREs leads to repression of the late promoter in a sequence-specific and titratable manner, resulting in a delay in late gene expression. These observations led to a model in which the late promoter is repressed at early times after infection by NRs, with this repression being relieved by titration of these repressors through simian virus 40 (SV40) genome replication to high copy number. Here, we tested this model in the context of the viral life cycle. SV40 genomes containing mutations in either or both HREs that significantly reduce NR binding without altering the coding of any proteins were constructed. Competition for replication between mutant and wild-type viruses in low-multiplicity coinfections indicated that the +1 HRE offered a significant selective advantage to the virus within a few cycles of infection in African green monkey kidney cell lines CV-1, CV-1P, TC-7, MA-134, and Vero but not in CV-1PD′ cells. Interestingly, the +55 HRE offered a selective disadvantage in MA-134 cells but had no effect in CV-1, CV-1P, TC-7, Vero, and CV-1PD′ cells. Thus, we conclude that these HREs are biologically important to the virus, but in a cell type-specific manner.

Sign in / Sign up

Export Citation Format

Share Document