scholarly journals Chicken ovalbumin upstream promoter transcription factors act as auxiliary cofactors for hepatocyte nuclear factor 4 and enhance hepatic gene expression.

1997 ◽  
Vol 17 (5) ◽  
pp. 2790-2797 ◽  
Author(s):  
E Ktistaki ◽  
I Talianidis
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Hormone Receptors ◽  
Physical Interaction ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Upstream Promoter ◽  
Hepatocyte Nuclear Factor 4 ◽  
Chicken Ovalbumin

Chicken ovalbumin upstream promoter transcription factors (COUP-TFs) strongly inhibit transcriptional activation mediated by nuclear hormone receptors, including hepatocyte nuclear factor 4 (HNF-4). COUP-TFs repress HNF-4-dependent gene expression by competition with HNF-4 for common binding sites found in several regulatory regions. Here we show that promoters, such as the HNF-1 promoter, which are recognized by HNF-4 but not by COUP-TFs are activated by COUP-TFI and COUP-TFII in conjunction with HNF-4 more than 100-fold above basal levels, as opposed to about 8-fold activation by HNF-4 alone. This enhancement was strictly dependent on an intact HNF-4 E domain. In vitro and in vivo evidence suggests that COUP-TFs enhance HNF-4 activity by a mechanism that involves their physical interaction with the amino acid 227 to 271 region of HNF-4. Our results indicate that in certain promoters, COUP-TFs act as auxiliary cofactors for HNF-4, orienting the HNF-4 activation domain in a more efficient configuration to achieve enhanced transcriptional activity. These findings provide new insights into the regulatory functions of COUP-TFs, suggesting their involvement in the initial activation and subsequent high-level expression of hepatic regulators, as well as in the positive and negative modulation of downstream target genes.

scholarly journals TRAP/SMCC/Mediator-Dependent Transcriptional Activation from DNA and Chromatin Templates by Orphan Nuclear Receptor Hepatocyte Nuclear Factor 4

2002 ◽  
Vol 22 (15) ◽  
pp. 5626-5637 ◽  
Author(s):  
Sohail Malik ◽  
Annika E. Wallberg ◽  
Yun Kyoung Kang ◽  
Robert G. Roeder
Keyword(s):  
Nuclear Receptor ◽  
Transcriptional Activation ◽  
Molecular Mechanisms ◽  
Strong Dependence ◽  
Physical Interaction ◽  
Nuclear Factor ◽  
Orphan Nuclear Receptor ◽  
Hepatocyte Nuclear Factor ◽  
Hepatocyte Nuclear Factor 4

ABSTRACT The orphan nuclear receptor hepatocyte nuclear factor 4 (HNF-4) regulates the expression of many liver-specific genes both during development and in the adult animal. Towards understanding the molecular mechanisms by which HNF-4 functions, we have established in vitro transcription systems that faithfully recapitulate HNF-4 activity. Here we have focused on the coactivator requirements for HNF-4, especially for the multicomponent TRAP/SMCC/Mediator complex that has emerged as the central regulatory module of the transcription apparatus. Using a system that has been reconstituted from purified transcription factors, as well as one consisting of unfractionated nuclear extract from which TRAP/SMCC/Mediator has been depleted by specific antibodies, we demonstrate a strong dependence of HNF-4 function on this coactivator. Importantly, we further show a TRAP/SMCC/Mediator-dependence for HNF-4 transcriptional activation from chromatin templates. The latter involves cooperation with the histone acetyltransferase-containing coactivator p300, in accord with a synergistic mode of action of the two divergent coactivators. We also show that HNF-4 and TRAP/SMCC/Mediator can interact physically. This interaction likely involves primary HNF-4 activation function 2 (AF-2)-dependent interactions with the TRAP220 subunit of TRAP/SMCC/Mediator and secondary (AF-2-independent) interactions with TRAP170/RGR1. Finally, recruitment experiments using immobilized templates strongly suggest that the functional consequences of the physical interaction probably are manifested at a postrecruitment step in the activation pathway.

scholarly journals Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and hepatocyte nuclear factor 4gamma (HNF-4gamma) and HNF-4alpha regulate the bovine growth hormone receptor 1A promoter through a common DNA element

2004 ◽  
Vol 32 (3) ◽  
pp. 947-961 ◽  
Author(s):  
Q Xu ◽  
N Walther ◽  
H Jiang
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Growth Hormone Receptor ◽  
Bovine Liver ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Hybrid Analysis ◽  
Factor Ii ◽  
Upstream Promoter ◽  
Chicken Ovalbumin

The growth hormone receptor (GHR) 1A promoter is responsible for transcription of the liver-specific GHR mRNA variant 1A in several mammalian species. We previously found that the region between nucleotide -218 and nucleotide -151 (relative to the major transcription start site) of the bovine GHR 1A promoter contained a binding site between -196 and -178 for the liver-enriched transcription factor hepatocyte nuclear factor 4alpha (HNF-4alpha) and that the same region might also interact with additional transcription factors in the liver. Using the -218/-151 region as bait to screen a bovine liver cDNA library in a yeast one-hybrid analysis, we identified chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and HNF-4gamma, as well as HNF-4alpha, as binding proteins to the -218/-151 region. These binding proteins were also identified in a second yeast one-hybrid analysis using the -196/-178 region as bait, suggesting that COUP-TFII, HNF-4gamma and HNF-4alpha all bind to the -196/-178 region. Electrophoretic mobility shift assays confirmed the ability of these three transcription factors in bovine liver nuclear extracts to interact with the -196/-178 region. These interactions also appeared to exist in vivo, as the GHR 1A promoter containing the -196/-178 region could be recovered by immunoprecipitation of the bovine liver chromatin with antibody against COUP-TFII, HNF-4gamma or HNF-4alpha. In co-transfection analyses, each of these three transcription factors could activate GHR 1A promoter and the activation was dependent on the -196/-178 region. These results together identify COUP-TFII, HNF-4gamma and HNF-4alpha as transcription factors regulating GHR 1A promoter activity through binding to a common DNA element.

Antagonism between apolipoprotein AI regulatory protein 1, Ear3/COUP-TF, and hepatocyte nuclear factor 4 modulates apolipoprotein CIII gene expression in liver and intestinal cells

1992 ◽  
Vol 12 (4) ◽  
pp. 1708-1718
Author(s):  
M Mietus-Snyder ◽  
F M Sladek ◽  
G S Ginsburg ◽  
C F Kuo ◽  
J A Ladias ◽  
...  
Keyword(s):  
Gene Expression ◽  
Regulatory Protein ◽  
Lipid Binding ◽  
Hepatic Tissue ◽  
Nuclear Factor ◽  
Apolipoprotein Ai ◽  
Hepatocyte Nuclear Factor ◽  
Apolipoprotein Ciii ◽  
Caco2 Cells ◽  
Hepatocyte Nuclear Factor 4

Apolipoprotein CIII (apoCIII), a lipid-binding protein involved in the transport of triglycerides and cholesterol in the plasma, is synthesized primarily in the liver and the intestine. A cis-acting regulatory element, C3P, located at -90 to -66 upstream from the apoCIII gene transcriptional start site (+1), is necessary for maximal expression of the apoCIII gene in human hepatoma (HepG2) and intestinal carcinoma (Caco2) cells. This report shows that three members of the steroid receptor superfamily of transcription factors, hepatocyte nuclear factor 4 (HNF-4), apolipoprotein AI regulatory protein 1 (ARP-1), and Ear3/COUP-TF, act at the C3P site. HNF-4 activates apoCIII gene expression in HepG2 and Caco2 cells, while ARP-1 and Ear3/COUP-TF repress its expression in the same cells. HNF-4 activation is abolished by increasing amounts of ARP-1 or Ear3/COUP-TF, and repression by ARP-1 or Ear3/COUP-TF is alleviated by increasing amounts of HNF-4. HNF-4 and ARP-1 bind with similar affinities to the C3P site, suggesting that their opposing transcriptional effects may be mediated by direct competition for DNA binding. HNF-4 and ARP-1 mRNAs are present within the same cells in the liver and intestine, and protein extracts from hepatic tissue, HepG2, and Caco2 cells contain significantly more HNF-4 than ARP-1 or Ear3/COUP-TF binding activities. These findings suggest that the transcription of the apoCIII gene in vivo is dependent, at least in part, upon the intracellular balance of these positive and negative regulatory factors.

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