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.

Murine chromosomal location of eight members of the hepatocyte nuclear factor 3/fork head winged helix family of transcription factors

Genomics ◽  
1995 ◽  
Vol 25 (2) ◽  
pp. 388-393 ◽  
Author(s):  
Karen B. Avraham ◽  
Colin Fletcher ◽  
David G. Overdier ◽  
Derek E. Clevidence ◽  
Eseng Lai ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Chromosomal Location ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Winged Helix ◽  
Fork Head

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.

The binding of fork head proteins to DNA is partly determined by cooperation of bases

2006 ◽  
Vol 1 (4) ◽  
pp. 594-608
Author(s):  
Václav Mach
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Binding Sites ◽  
In Silico ◽  
Dna Recognition ◽  
Simple Algorithm ◽  
Fork Head ◽  
Statistical Algorithm ◽  
On Line ◽  
Negative Base

AbstractOur previous study revealed that DNA recognition by the insect Fork head transcription factors depends on specific combinations of neighboring bases, a phenomenon called the base cooperation effect. This study presents a simple algorithm designed for in silico investigation of the base cooperation effect. The algorithm measures and evaluates observed and expected frequencies of various base combinations within a set of aligned binding sites. Consequently, statistically significant differences between the observed and expected frequencies are interpreted as evidence of either positive or negative base cooperation effect. Our current results suggest that the base cooperation affects DNA binding of the vertebrate members of the Fork head family, similarly to their insect homologies.The statistical algorithm used in this study is available on line (http://blast.entu.cas.cz/bias/index.htm).

Hepatocyte nuclear factor 3 beta contains two transcriptional activation domains, one of which is novel and conserved with the Drosophila fork head protein

1992 ◽  
Vol 12 (9) ◽  
pp. 3723-3732
Author(s):  
L Pani ◽  
D G Overdier ◽  
A Porcella ◽  
X Qian ◽  
E Lai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Carboxyl Terminus ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Amino Terminal ◽  
Fork Head ◽  
Fourth Segment ◽  
Region Ii

The hepatocyte nuclear factor 3 (HNF-3) gene family is composed of three proteins (alpha, beta, and gamma) that are transcription factors involved in the coordinate expression of several liver genes. All three proteins share strong homology in their DNA binding domains (region I) and are able to recognize the same DNA sequence. They also possess two similar stretches of amino acids at the carboxyl terminus (regions II and III) and a fourth segment of homology at the amino terminus (region IV). Furthermore, the HNF-3 proteins demonstrate homology with the Drosophila homeotic gene fork head in regions I, II, and III, suggesting that HNF-3 may be its mammalian homolog. In order to define HNF-3 beta protein domains involved in transcriptional activation, we have used a reporter gene, whose transcription is dependent on HNF-3 binding, for hepatoma cell cotransfection assays with expression vectors that produced different truncated HNF-3 beta proteins. A position-independent activation domain which contained conserved regions II and III was identified at the carboxyl terminus of the HNF-3 beta protein (amino acids 361 to 458). Moreover, site-directed mutations that altered the sequences within regions II and III demonstrated their importance to transactivation. The region II-III domain does not possess amino acid sequences in common with other transcription factors and may define a novel activation motif. HNF-3 beta amino-terminal sequences defined by conserved region IV also contributed to transactivation, but region IV activity required the participation of the region II-III domain. Region IV is abundant in serine amino acids and contains two putative casein kinase I phosphorylation sites, a feature similar to protein motifs described for the transcription factors Pit-1/GHF-1 and HNF-1.

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 3 beta contains two transcriptional activation domains, one of which is novel and conserved with the Drosophila fork head protein.

1992 ◽  
Vol 12 (9) ◽  
pp. 3723-3732 ◽  
Author(s):  
L Pani ◽  
D G Overdier ◽  
A Porcella ◽  
X Qian ◽  
E Lai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Carboxyl Terminus ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Amino Terminal ◽  
Fork Head ◽  
Fourth Segment ◽  
Region Ii

The hepatocyte nuclear factor 3 (HNF-3) gene family is composed of three proteins (alpha, beta, and gamma) that are transcription factors involved in the coordinate expression of several liver genes. All three proteins share strong homology in their DNA binding domains (region I) and are able to recognize the same DNA sequence. They also possess two similar stretches of amino acids at the carboxyl terminus (regions II and III) and a fourth segment of homology at the amino terminus (region IV). Furthermore, the HNF-3 proteins demonstrate homology with the Drosophila homeotic gene fork head in regions I, II, and III, suggesting that HNF-3 may be its mammalian homolog. In order to define HNF-3 beta protein domains involved in transcriptional activation, we have used a reporter gene, whose transcription is dependent on HNF-3 binding, for hepatoma cell cotransfection assays with expression vectors that produced different truncated HNF-3 beta proteins. A position-independent activation domain which contained conserved regions II and III was identified at the carboxyl terminus of the HNF-3 beta protein (amino acids 361 to 458). Moreover, site-directed mutations that altered the sequences within regions II and III demonstrated their importance to transactivation. The region II-III domain does not possess amino acid sequences in common with other transcription factors and may define a novel activation motif. HNF-3 beta amino-terminal sequences defined by conserved region IV also contributed to transactivation, but region IV activity required the participation of the region II-III domain. Region IV is abundant in serine amino acids and contains two putative casein kinase I phosphorylation sites, a feature similar to protein motifs described for the transcription factors Pit-1/GHF-1 and HNF-1.

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