scholarly journals Modulation of hepatocyte nuclear factor-4α function by the peroxisome-proliferator-activated receptor-γ co-activator-1α in the acute-phase response

2008 ◽  
Vol 415 (2) ◽  
pp. 289-296 ◽  
Author(s):  
Zhongyan Wang ◽  
Peter A. Burke
Keyword(s):  
Dna Binding ◽  
Binding Sites ◽  
Acute Phase Response ◽  
Peroxisome Proliferator ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Binding Ability ◽  
Peroxisome Proliferator Activated Receptor ◽  
Cytokine Treatment ◽  
Hepatocyte Nuclear Factor 4Α

HNF-4α (hepatocyte nuclear factor-4α) is a key regulator of liver-specific gene expression. To understand the mechanisms governing the regulation of HNF-4α function during the APR (acute-phase response), the effects of transcription co-activators, including p300, PGC-1α (peroxisome-proliferator-activated receptor-γ co-activator-1α) and SRC (steroid receptor co-activator)-1α were investigated in an injury cell model. We have shown previously that the HNF-4α-sensitive APR genes ApoB (apolipoprotein B), TTR (transthyretin) and α1-AT (α1-antitrypsin) were regulated at the DNA binding and transcriptional levels after cytokine stimulation. We now show that co-activators have a differential impact on the transactivation of HNF-4α-sensitive genes via HNF-4α-binding sites in ApoB, TTR or α1-AT promoters. PGC-1α strongly enhances the transactivation of ApoB and α1-AT and, to a lesser extent, of TTR, whereas SRC-1α and p300 only have a weak or no effect on these three genes. More importantly, it was found that PGC-1α has a novel role in the modulation of the binding ability of HNF-4α in response to cytokine treatment. Using in vitro and in vivo approaches, electrophoretic mobility-shift and chromatin immunoprecipitation assays, we demonstrate that the reduced HNF-4α–DNA binding ability induced by cytokines is eliminated by overexpression of PGC-1α. Cytokine treatment does not significantly alter the protein levels of HNF-4α and PGC-1α, but it does reduce the recruitment of PGC-1α to HNF-4α-binding sites and thereby decreases transcriptional activity. These results establish the importance of PGC-1α for HNF-4α function and describe a new HNF-4α-dependent regulatory mechanism that is involved in the response to injury.

scholarly journals Hepatocyte nuclear factor-4alpha mediates the stimulatory effect of peroxisome proliferator-activated receptor gamma co-activator-1alpha (PGC-1alpha) on glucose-6-phosphatase catalytic subunit gene transcription in H4IIE cells

2003 ◽  
Vol 369 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Jared N. BOUSTEAD ◽  
Beth T. STADELMAIER ◽  
Angela M. EEDS ◽  
Peter O. WIEBE ◽  
Christina A. SVITEK ◽  
...  
Keyword(s):  
Fusion Gene ◽  
Catalytic Subunit ◽  
Peroxisome Proliferator ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Peroxisome Proliferator Activated Receptor ◽  
H4iie Cells ◽  
Evolutionarily Conserved ◽  
Hepatocyte Nuclear Factor 4Α ◽  
Hepatocyte Nuclear Factor 4Alpha

It has recently been shown that adenoviral-mediated expression of peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1 α) in hepatocytes stimulates glucose-6-phosphatase catalytic subunit (G6Pase) gene expression. A combination of fusion gene, gel retardation and chromatin immunoprecipitation assays revealed that, in H4IIE cells, PGC-1α mediates this stimulation through an evolutionarily conserved region of the G6Pase promoter that binds hepatocyte nuclear factor-4α.

scholarly journals Phosphorylation of Ser158 regulates inflammatory redox-dependent hepatocyte nuclear factor-4α transcriptional activity

2006 ◽  
Vol 394 (2) ◽  
pp. 379-387 ◽  
Author(s):  
Hongtao Guo ◽  
Chengjiang Gao ◽  
Zhiyong Mi ◽  
Philip Y. Wai ◽  
Paul C. Kuo
Keyword(s):  
Dna Binding ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
P38 Kinase ◽  
Mobility Shift ◽  
Transactivation Potential ◽  
Hepatocyte Nuclear Factor 4Α

In IL-1β (interleukin 1β)-stimulated rat hepatocytes exposed to superoxide, we have previously identified an IRX (inflammatory redox)-sensitive DR1 [direct repeat of RG(G/T)TCA with one base spacing] cis-acting activator element (nt –1327 to –1315) in the iNOS (inducible nitric oxide synthase) promoter: AGGTCAGGGGACA. The corresponding transcription factor was identified to be HNF4α (hepatocyte nuclear factor-4α). HNF4α DNA binding activity and transactivation potential are tightly regulated by its state of phosphorylation. However, the functional consequences of IRX-mediated post-translational phosphorylation of HNF4α have not been well characterized. In the setting of IL-1β+H2O2, HNF4α functional activity is associated with a unique serine/threonine phosphorylation pattern. This indicates that an IRX-sensitive serine/threonine kinase pathway targets HNF4α to augment hepatocyte iNOS transcription. In the present study, following identification of phosphorylated residues in HNF4α, serial mutations were performed to render the target residues phosphorylation-resistant. Electrophoretic mobility-shift assays and transient transfection studies utilizing the iNOS promoter showed that the S158A mutation ablates IRX-mediated HNF4α DNA binding and transactivation. Gain-of-function mutation with the S158D phosphomimetic HNF4α vector supports a critical role for Ser158 phosphorylation. In vitro phosphorylation and kinase inhibitor studies implicate p38 kinase activity. Our results indicate that p38 kinase-mediated Ser158 phosphorylation is essential for augmentation of the DNA binding and transactivation potential of HNF4α in the presence of IL-1β+H2O2. This pathway results in enhanced iNOS expression in hepatocytes exposed to pro-inflammatory cytokines and oxidative stress.

scholarly journals Overproduction of a truncated hepatocyte nuclear factor 3 protein inhibits expression of liver-specific genes in hepatoma cells.

1995 ◽  
Vol 15 (10) ◽  
pp. 5453-5460 ◽  
Author(s):  
V Vallet ◽  
B Antoine ◽  
P Chafey ◽  
A Vandewalle ◽  
A Kahn
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Sites ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Hepatoma Cells ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Regulatory Regions ◽  
Truncated Protein ◽  
Fork Head

Transcription of hepatocyte-specific genes requires the interaction of their regulatory regions with several nuclear factors. Among them is the hepatocyte nuclear factor 3 (HNF3) family, composed of the HNF3 alpha, HNF3 beta, and HNF3 gamma proteins, which are expressed in the liver and have very similar fork head DNA binding domains. The regulatory regions of numerous hepatocyte-specific genes contain HNF3 binding sites. We examined the role of HNF3 proteins in the liver-specific phenotype by turning off the HNF3 activity in well-differentiated mhAT3F hepatoma cells. Cells were stably transfected with a vector allowing the synthesis of an HNF3 beta fragment consisting of the fork head DNA binding domain without the transactivating amino- and carboxy-terminal domains. The truncated protein was located in the nuclei of cultured hepatoma cells and competed with endogenous HNF3 proteins for binding to cognate DNA sites. Overproduction of this truncated protein, lacking any transactivating activity, induced a dramatic decrease in the expression of liver-specific genes, including those for albumin, transthyretin, transferrin, phosphoenolpyruvate carboxykinase, and aldolase B, whereas the expression of the L-type pyruvate kinase gene, containing no HNF3 binding sites, was unaltered. Neither were the concentrations of various liver-specific transcription factors (HNF3, HNF1, HNF4, and C/EBP alpha) affected. In partial revertants, with a lower ratio of truncated to full-length endogenous HNF3 proteins, previously extinguished genes were re-expressed. Thus, the transactivating domains of HNF3 proteins are needed for the proper expression of a set of liver-specific genes but not for expression of the genes encoding transcription factors found in differentiated hepatocytes.

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