scholarly journals Hepatocyte Nuclear Factor 4 Provokes Expression of Epithelial Marker Genes, Acting As a Morphogen in Dedifferentiated Hepatoma Cells

1998 ◽  
Vol 140 (4) ◽  
pp. 935-946 ◽  
Author(s):  
Gerald F. Späth ◽  
Mary C. Weiss
Keyword(s):  
Epithelial Cell ◽  
Hepatoma Cells ◽  
Stable Expression ◽  
Junctional Complex ◽  
Cell Phenotype ◽  
Marker Genes ◽  
Specific Gene ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
E Cadherin

Abstract. We have recently shown that stable expression of an epitope-tagged cDNA of the hepatocyte- enriched transcription factor, hepatocyte nuclear factor (HNF)4, in dedifferentiated rat hepatoma H5 cells is sufficient to provoke reexpression of a set of hepatocyte marker genes. Here, we demonstrate that the effects of HNF4 expression extend to the reestablishment of differentiated epithelial cell morphology and simple epithelial polarity. The acquisition of epithelial morphology occurs in two steps. First, expression of HNF4 results in reexpression of cytokeratin proteins and partial reestablishment of E-cadherin production. Only the transfectants are competent to respond to the synthetic glucocorticoid dexamethasone, which induces the second step of morphogenesis, including formation of the junctional complex and expression of a polarized cell phenotype. Cell fusion experiments revealed that the transfectant cells, which show only partial restoration of E-cadherin expression, produce an extinguisher that is capable of acting in trans to downregulate the E-cadherin gene of well-differentiated hepatoma cells. Bypass of this repression by stable expression of E-cadherin in H5 cells is sufficient to establish some epithelial cell characteristics, implying that the morphogenic potential of HNF4 in hepatic cells acts via activation of the E-cadherin gene. Thus, HNF4 seems to integrate the genetic programs of liver-specific gene expression and epithelial morphogenesis.

scholarly journals The transcriptional activator hepatocyte nuclear factor 6 regulates liver gene expression.

1996 ◽  
Vol 16 (11) ◽  
pp. 6273-6284 ◽  
Author(s):  
U Samadani ◽  
R H Costa
Keyword(s):  
Gene Expression ◽  
Epithelial Cell ◽  
Dna Binding ◽  
Target Genes ◽  
Site Directed Mutagenesis ◽  
Epithelial Cell Line ◽  
Homeodomain Protein ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Fatty Acid Binding

The hepatocyte nuclear factor 3(alpha) (HNF-3(alpha)), -3(beta), and -3(gamma) proteins share homology in the winged-helix/fork head DNA binding domain and mediate hepatocyte-enriched transcription of numerous genes whose expression is necessary for organ function. In this work, we identify a liver-enriched transcription factor, HNF-6, which recognizes the -138 to -126 region of the HNF-3(beta) promoter and binds the original HNF-3 site of the transthyretin promoter (-94 to -106). We show that HNF-6 and HNF-3 possess different DNA binding specificities by competition and methylation interference studies and are immunologically distinct. Site-directed mutagenesis of the HNF-6 sites in the HNF-3(beta) and transthyretin promoters diminishes reporter gene expression, suggesting that HNF-6 activates transcription of these promoters. Using the HNF-6 binding sequence DHWATTGAYTWWD (where W = A or T, Y = T or C, H is not G, and D is not C) determined by sequence comparison and methylation interference, we predicted that HNF-6 will bind to 22 additional hepatocyte-enriched genes. Of these potential target genes, we selected seven of the HNF-6 binding sequences and demonstrated that they bind the HNF-6 protein. These include promoter sequences from alpha-2 urinary globulin, alpha-1 antitrypsin, cytochrome P-450 2C13, L-type 6-phosphofructo-2-kinase, mouse major urinary protein, tryptophan oxygenase, and alpha-fetoprotein genes. HNF-6 binding activity was also found in the intestinal epithelial cell line HT29, and potential HNF-6 binding sites were present in intestinal sucrase isomaltase, cdx-2 homeodomain protein, and intestinal fatty acid binding protein promoter regions. These studies suggest that HNF-6 may regulate hepatocyte-specific genes and may play a role in epithelial cell differentiation of gut endoderm via regulation of HNF-3(beta).

scholarly journals Functional Activity of Human Hepatoma Cells Transfected with Adenovirus-Mediated Hepatocyte Nuclear Factor (HNF)-4 Gene

2004 ◽  
Vol 13 (4) ◽  
pp. 393-404 ◽  
Author(s):  
Takafumi Naiki ◽  
Masahito Nagaki ◽  
Yoshihiro Shidoji ◽  
Hisanori Kojima ◽  
Hisataka Moriwaki
Keyword(s):  
Functional Activity ◽  
Hepatoma Cells ◽  
Nuclear Factor ◽  
Human Hepatoma ◽  
Hepatocyte Nuclear Factor ◽  
Human Hepatoma Cells

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.

scholarly journals Liver-enriched transcription factors uncoupled from expression of hepatic functions in hepatoma cell lines.

1997 ◽  
Vol 17 (11) ◽  
pp. 6311-6320 ◽  
Author(s):  
D Chaya ◽  
C Fougère-Deschatrette ◽  
M C Weiss
Keyword(s):  
Transcription Factors ◽  
Hepatoma Cell ◽  
Hepatoma Cells ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Hepatic Differentiation ◽  
Hepatoma Cell Lines ◽  
Differentiated Cells ◽  
Heritable Phenotype ◽  
Nuclear Factor 1

Among the liver-enriched transcription factors identified to date, only expression of hepatocyte nuclear factor 4 (HNF4) and hepatocyte nuclear factor 1 (HNF1) is in strict correlation with hepatic differentiation in cultured rat hepatoma cells. Indeed, differentiated hepatoma cells that stably express an extensive set of adult hepatic functions express liver-enriched transcription factors, while dedifferentiated cells that have lost expression of all these hepatic functions no longer express HNF4 and HNF1. We describe a new heritable phenotype, designated as uncoupled, in which there is a spontaneous dissociation between the expression of these transcription factors and that of the hepatic functions. Cells presenting this phenotype, isolated from differentiated hepatoma cells, cease to accumulate all transcripts coding for hepatic functions but nevertheless maintain expression of HNF4 and HNF1. Transitory transfection experiments indicate that these two factors present in these cells have transcriptional activity similar to that of differentiated hepatoma cells. Characterization of the appropriate intertypic cell hybrids demonstrates that this new phenotype is recessive to the dedifferentiated state and fails to be complemented by differentiated cells. These results indicate the existence of mechanisms that inhibit transcription of genes coding for hepatocyte functions in spite of the presence of functional HNF4 and HNF1. Cells of the uncoupled phenotype present certain properties of oval cells described for pathological states of the liver.

scholarly journals Inhibition of hepatocyte nuclear factor 4 transcriptional activity by the nuclear factor κB pathway

2006 ◽  
Vol 398 (3) ◽  
pp. 439-450 ◽  
Author(s):  
Varvara Nikolaidou-Neokosmidou ◽  
Vassilis I. Zannis ◽  
Dimitris Kardassis
Keyword(s):  
Gene Expression ◽  
Inflammatory Cytokine ◽  
Transcriptional Activity ◽  
Binding Protein ◽  
Nuclear Factor Κb ◽  
Specific Gene ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Response Element ◽  
Hepatocyte Nuclear Factor 4

HNF-4 (hepatocyte nuclear factor 4) is a key regulator of liver-specific gene expression in mammals. We have shown previously that the activity of the human APOC3 (apolipoprotein C-III) promoter is positively regulated by the anti-inflammatory cytokine TGFβ (transforming growth factor β) and its effectors Smad3 (similar to mothers against decapentaplegic 3) and Smad4 proteins via physical and functional interactions between Smads and HNF-4. We now show that the pro-inflammatory cytokine TNFα (tumour necrosis factor α) antagonizes TGFβ for the regulation of APOC3 gene expression in hepatocytes. TNFα was a strong inhibitor of the activity of apolipoprotein promoters that harbour HNF-4 binding sites and this inhibition required HNF-4. Using specific inhibitors of TNFα-induced signalling pathways, it was shown that inhibition of the APOC3 promoter by TNFα involved NF-κB (nuclear factor κB). Latent membrane protein 1 of the Epstein–Barr virus, which is an established potent activator of NF-κB as well as wild-type forms of various NF-κB signalling mediators, also inhibited strongly the APOC3 promoter and the transactivation function of HNF-4. TNFα had no effect on the stability or the nuclear localization of HNF-4 in HepG2 cells, but inhibited the binding of HNF-4 to the proximal APOC3 HRE (hormone response element). Using the yeast-transactivator-GAL4 system, we showed that both AF-1 and AF-2 (activation functions 1 and 2) of HNF-4 are inhibited by TNFα and that this inhibition was abolished by overexpression of different HNF-4 co-activators, including PGC-1 (peroxisome-proliferator-activated-receptor-γ co-activator 1), CBP [CREB (cAMP-response-element-binding protein) binding protein] and SRC3 (steroid receptor co-activator 3). In summary, our findings indicate that TNFα, or other factors that trigger an NF-κB response in hepatic cells, inhibit the transcriptional activity of the APOC3 and other HNF-4-dependent promoters and that this inhibition could be accounted for by a decrease in DNA binding and the down-regulation of the transactivation potential of the AF-1 and AF-2 domains of HNF-4.

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