Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A variety of gene constructs containing carp beta-actin regulatory sequences were tested for their ability to drive transient expression of the chloramphenicol acetyltransferase reporter gene in 3 fish cell lines: carp epithelial cells (EPC), rainbow trout hepatoma cells (RTH149), and rainbow trout fibroblasts (RTG2). The constructs showed a wide variation in their levels of expression, and there were significant differences in the effects of transcriptional elements in the 3 cell lines. Sequences that enhanced expression in EPC cells were inhibitory in RTH149 and RTG2 cells. All cell lines exhibited the presence of nuclear trans-acting factors that could bind to implicated transcriptional control elements. On the basis of the cell culture results, selected constructs were examined for activity in early carp development. Constructs active in embryos and fry were further tested and found to express transgenes in adult fish.
Mol Mar Biol Biotechnol
PMID:Selection of promoters for gene transfer into fish. 130 23

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.
Mol Cell Biol 1992 Apr
PMID: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. 131 68

Transcriptional activation of the murine Cyp1a-1 (cytochrome P(1)450) gene by inducers such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (dioxin) requires the aromatic hydrocarbon (Ah) receptor and the interaction of an inducer-receptor complex with one or more of the Ah-responsive elements (AhREs) located about 1 kb upstream from the transcriptional initiation site. We find that treatment of mouse hepatoma Hepa-1 cells with 2-aminopurine, an inhibitor of protein kinase activity, inhibits CYP1A1 mRNA induction by TCDD as well as the concomitant increase in CYP1A1 enzyme activity. Formation of DNA-protein complexes between the Ah receptor and its AhRE target is also inhibited by 2-aminopurine, as determined by gel mobility shift assays. Phosphorylation is required for the formation of Ah receptor-specific complexes, since in vitro dephosphorylation of nuclear extracts from TCDD-treated Hepa-1 cells abolishes the capacity of the Ah receptor to form specific complexes with its cognate AhRE sequences. To determine whether any one of several known protein kinases was involved in the transcriptional regulation of the Cyp1a-1 gene, we treated Hepa-1 cells with nine other protein kinase inhibitors prior to induction with TCDD; nuclear extracts from these cells were analyzed for their capacity to form specific DNA-protein complexes. Only extracts from cells treated with staurosporine, a protein kinase C inhibitor, were unable to form these complexes. In addition, staurosporine completely inhibited CYP1A1 mRNA induction by TCDD. Depletion of protein kinase C by prolonged treatment with phorbol ester led to the complete suppression of CYP1A1 mRNA induction by TCDD. We conclude that (i) phosphorylation is necessary for the formation of a transcriptional complex and for transcriptional activation of the Cyp1a-1 gene; (ii) the phosphorylation site(s) exists on at least one of the proteins constituting the transcriptional complex, possibly the Ah receptor itself; and (iii) the enzyme responsible for the phosphorylation is likely to be protein kinase C.
Mol Cell Biol 1992 Apr
PMID:Dioxin-dependent activation of murine Cyp1a-1 gene transcription requires protein kinase C-dependent phosphorylation. 131 72

In the rat, expression of the CYP1A1 gene is closely associated with arylhydrocarbon hydroxylase (AHH) enzyme activity. AHH is an inducile enzyme activity known to play an important role in the bioactivation of polycyclic aromatic hydrocarbons (PAHs) to mutagenic and carcinogenic metabolites. PAH-induced expression of the CYP1A1 gene appears to be regulated by several trans-acting factors, including the Ah receptor and the 4S PAH-binding protein. In this study, we used the PAH isomers benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) to further evaluate the role of the 4S PAH-binding protein in induction of the CYP1A1 gene in H4-II-E rat hepatoma cells. Although BaP is believed to bind to both the Ah receptor and the 4S protein, BeP has been reported to bind exclusively to the 4S protein. The results of the study presented here indicate that BaP and BeP induce the expression of the CYP1A1 gene, as measured by ethoxyresorufin O-deethylase (EROD) activity, in a concentration-dependent manner. However, BaP is about 25 times as potent as BeP in inducing EROD activity in these cells. Slot-blot analysis of total RNA isolated from these cells indicated that BeP, BaP, and 3-methylcholanthrene increased the level of CYP1A1 mRNA expression. Sucrose-gradient analysis of BeP binding activity indicated that BeP bound with high affinity to the 4S PAH-binding protein, but not to the Ah receptor. These results suggest that the 4S protein may play a role in the PAH-induced expression of the CYP1A1 gene in rat H4-II-E cells.
Mol Carcinog 1992
PMID:Induction of CYP1A1 gene expression in H4-II-E rat hepatoma cells by benzo[e]pyrene. 131 59

The gene coding for apolipoprotein AI (apoAI), a lipid binding protein involved in the transport of cholesterol and other lipids in the plasma, is expressed in mammals predominantly in the liver and the intestine. Liver-specific expression is controlled by synergistic interactions between transcription factors bound to three separate sites, sites A (-214 to -192), B (-169 to -146), and C (-134 to -119), within a powerful liver-specific enhancer located between nucleotides -222 and -110 upstream of the apoAI gene transcription start site (+1). Previous studies in our laboratory have shown that ARP-1, a member of the nuclear receptor superfamily whose ligand is unknown (orphan receptor), binds to site A and represses transcription of the apoAI gene in liver cells. In a more recent series of experiments, we found that site A is a retinoic acid (RA) response element that responds preferentially to the recently identified RA-responsive receptor RXR alpha over the previously characterized RA receptors RAR alpha and RAR beta. In this study we investigated the combined effects of ARP-1 and RXR alpha on apoAI gene expression in liver cells. Transient transfection assays showed that site A is necessary and sufficient for RXR alpha-mediated transactivation of the apoAI gene basal promoter in human hepatoma HepG2 cells in the presence of RA and that this transactivation is abolished by increasing amounts of cotransfected ARP-1. Electrophoretic mobility shift assays and subsequent Scatchard analysis of the data revealed that ARP-1 and RXR alpha bind to site A with similar affinities. These assays also revealed that ARP-1 and RXR alpha bind to site A as heterodimers with an affinity approximately 10 times greater than that of either ARP-1 or RXR alpha alone. Further transfection assays in HepG2 cells, using as a reporter a construct containing the apoAI gene basal promoter and its upstream regulatory elements (including site A) in their natural context, revealed that RXR alpha has very little effect on the levels of expression regardless of the presence or absence of RA. However, while ARP-1 alone or ARP-1 and RXR alpha together dramatically repress expression in the absence of RA, the repression by ARP-1 and RXR alpha together, but not ARP-1 alone, is almost completely alleviated in the presence of RA. These results indicate that transcriptional repression by ARP-1 sensitizes apoAI gene responsiveness to RXR alpha and RA and suggest that the magnitude of this responsiveness is regulated by the intracellular ratio of ARP-1 to RXR alpha. These observations raise the possibility that transcriptional repression is a general mechanism for switching gene transcription between alternative transcription activation pathways.
Mol Cell Biol 1992 Aug
PMID:Repression by ARP-1 sensitizes apolipoprotein AI gene responsiveness to RXR alpha and retinoic acid. 132 32

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.
Mol Cell Biol 1992 Sep
PMID:Hepatocyte nuclear factor 3 beta contains two transcriptional activation domains, one of which is novel and conserved with the Drosophila fork head protein. 132 4

The subcellular distribution and regulation of MAP kinase isoforms in chicken hepatoma DU249 cells was investigated with antibodies directed against peptides patterned after sequences in the mitogen-activated protein (MAP) kinases, sea star p44mpk, and rat p44erk1. MonoQ chromatography of cytosol from these cells afforded the resolution of at least four peaks of myelin basic protein (MBP) phosphotransferase activity, but only one of these (peak II) was stimulated in extracts from phorbol ester-treated cells. A 40- to 41-kDa (p41) doublet on Western blots detected with three different MAP kinase antibodies was coincident with peak II, and it probably corresponded to the avian homolog of p42mapk/erk2. Immunofluorescent studies with DU249 cells and chicken embryo fibroblasts revealed that most of the cross-reactive protein with at least two different MAP kinase antibodies was distributed in the nucleus. Subcellular fractionation studies confirmed a predominantly nuclear localization for p41 MAP kinase. Nocodazole arrest of DU249 cells was exploited for the detection of an M-phase-activated MBP kinase that was resolved from p41 MAP kinase by phenyl-Superose chromatography. Western blotting analysis with antibodies for the cdc2-encoded protein kinase and p13suc1-agarose binding studies allowed positive identification of this MBP kinase as p34cdc2.
Mol Biol Cell 1992 Jul
PMID:Immunological characterization of avian MAP kinases: evidence for nuclear localization. 132 21

We investigated the mechanism by which cyclic AMP (cAMP) induces gap junctional communication via cell-to-cell channels in a communication-deficient rat Morris hepatoma cell line. We found that under basal conditions, the cells transcribe cx43 at a low level but do not transcribe cx26 or cx32. Elevation of intracellular cAMP, which induced communication, increased cx43 mRNA 15- to 40-fold and the rate of cx43 transcription 6-fold. Cx43 protein was detected by immunostaining in junctions of only those cells in which communication had been induced. We found the regulation by cAMP also in other cell lines; namely, in those with a low basal level of cx43 mRNA.
Mol Biol Cell 1992 Aug
PMID:Transcription of the gene for the gap junctional protein connexin43 and expression of functional cell-to-cell channels are regulated by cAMP. 132 97

The role of protein synthesis in the control of phosphoenolpyruvate carboxykinase (PEPCK; 4.1.1.32) mRNA turnover was studied in FTO-2B rat hepatoma cells. A previous study demonstrated that incubation of these cells with cAMP prolongs the half-life of the otherwise short-lived PEPCK mRNA. The decay rate of PEPCK mRNA was also slowed in cells incubated with cycloheximide, but not in cells incubated with other translation inhibitors, such as puromycin or pactamycin, even though protein synthesis was inhibited 85-95% by these agents. No correlation was noted between the rate of L-[3H]valine incorporation into cellular proteins and PEPCK mRNA half-life, suggesting that protein synthesis per se is not required for breakdown of the mRNA. Exposure of cells to the translation initiation inhibitor pactamycin together with cycloheximide abolished the "slowing" effect of cycloheximide, and PEPCK mRNA decayed at the same rate as in cells incubated in the presence of pactamycin alone. In contrast, pactamycin did not reverse the effect of cAMP, and the mRNA decayed at the same slow rate in cells incubated in the presence of either (Bu)2cAMP alone or (Bu)2cAMP together with pactamycin. Since pactamycin promotes polysomes dissociation, these results suggest that cAMP enhances the stability of a polysome-free PEPCK mRNA. Furthermore, these results strongly indicate that neither the rapid decay of PEPCK mRNA nor the cAMP-mediated stabilization of the mRNA requires on-going protein synthesis.
Mol Endocrinol 1992 Sep
PMID:The role of protein synthesis in the decay of phosphoenolpyruvate carboxykinase messenger RNA. 133 75

Expression plasmids containing the human alpha 1-antitrypsin (alpha 1 AT) promoter fused to either adenine phosphoribosyltransferase (aprt) or xanthine-guanine phosphoribosyltransferase (gpt) coding sequences were sequentially introduced into APRT- HPRT- rat hepatoma cells. Stable transfectants expressing both transgenes were isolated and characterized. Nonexpressing variants were subsequently obtained by selecting against expression of one or both transgenes. Variants isolated by selecting against expression of either transgene alone generally displayed deficiency phenotypes in cis, as only three of 20 clones tested were affected for expression of alpha 1AT mRNA. In contrast, double selection yielded predominantly trans effects: 12 of 14 lines tested showed impaired ability to express their chromosomal alpha 1AT genes. Furthermore, expression of several other liver genes, including the gene encoding the HNF-1 trans-activator, was repressed in many of the variant lines. Thus, double selection using chimeric transgenes is a useful approach for generating variant cell lines deficient in expression of specific mammalian genes.
Somat Cell Mol Genet 1992 Jul
PMID:Direct selection of hepatoma cell variants deficient in alpha 1-antitrypsin gene expression. 133 97


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