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)

The rat tyrosine aminotransferase(TAT) gene promoter (nucleotides -350 to +1; TAT0.35) was able to sustain liver-specific expression both ex vivo in transient transfection (TAT-expressing H411EC3 hepatoma cells vs. TAT non-expressing CCL1.2 fibroblasts) and in in vitro transcription (rat liver vs. spleen crude nuclear extracts). In either case, the index of tissue specificity (6.2 and 6.7 in ex vivo and in vitro experiments, respectively) was close to that obtained with 10 Kb of TAT gene 5'-flanking sequences in transient transfection. Using computer-assisted search of homologies, DNase I footprinting, gel retardation and methylation interference assays, we showed that TAT0.35 sequences spanning nt -156 to -175 and nt -268 to -281 interacted with the liver enriched NF-1Liver (a member of the NF1 gene family) and HNF1 respectively, whereas those encompassing nt -57 to -85 and nt -283 to -288 interacted with the ubiquitous NF-Y and with ubiquitous 'CCAAT'-box binding factor(s), respectively. Competition studies in in vitro transcription carried out with wild type and mutated oligonucleotides, demonstrated that NF-Y cis-elements were crucial for basal TAT promoter activity, both in liver and spleen whereas NF1Liver and HNF1 were only efficient in the liver (supported approximately 60% and 30% of basal TAT0.35 activity respectively). Altogether, these results support the conclusion that TAT0.35 was able to sustain at least part of the liver specificity of TAT gene expression.
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PMID:Expression from the tyrosine aminotransferase promoter (nt -350 to +1) is liver-specific and dependent on the binding of both liver-enriched and ubiquitous trans-acting factors. 791 Dec 35

Hepatitis B viruses (hepadnaviruses) can cause chronic, productive infections of hepatocytes. Analyses of the enhancers and promoters of these viruses in cell lines have suggested a requirement of these elements for liver-enriched transcription factors. In this study, a minimum of seven factor-binding sites on the duck hepatitis B virus enhancer were detected by DNase I footprinting using duck liver nuclear extracts. Among the sites that were tentatively identified were one C/EBP-, one HNF1-, and two HNF3-binding sites. Mutations of the HNF1- and HNF3-like sites, which eliminated factor binding, as assessed by both DNase I footprinting and competitive gel shift assays, were evaluated for their effects on enhancer activity. Using a construct in which human growth hormone was expressed from the viral enhancer and core gene promoter, we found that all of the mutations, either alone or in combination, reduced expression two- to fourfold in LMH chicken hepatoma cells. The mutations in the HNF1 site and one of the HNF3 sites, when inserted into the intact viral genome, also suppressed virus RNA synthesis in primary hepatocyte cultures. Virus carrying the latter HNF3 mutation was also examined for its ability to infect and replicate in ducks. No significant inhibition of virus replication was observed in a short-term assay; however, virus with the HNF3 mutation was apparently unable to grow in the pancreas, a second site of duck hepatitis B virus replication in the duck.
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PMID:Identification of factor-binding sites in the duck hepatitis B virus enhancer and in vivo effects of enhancer mutations. 813 13

Angiotensinogen is shown to be produced by the liver and the hepatoma cell line HepG2. As a first step for understanding the molecular relationship between the transcriptional regulation of the angiotensinogen gene and the pathogenesis of hypertension, we have analyzed the basal promoter of the angiotensinogen gene. Chloramphenicol acetyltransferase (CAT) assays with 5'-deleted constructs showed that the proximal promoter region from -96 to +22 of the transcriptional start site was enough to express HepG2-specific CAT activity. Electrophoretic mobility shift assay and DNase I footprinting demonstrated that the liver- and HepG2-specific nuclear factor (angiotensinogen gene-activating factor [AGF2]) and ubiquitous nuclear factor (AGF3) bound to the proximal promoter element from -96 to -52 (angiotensinogen gene-activating element [AGE2]) and to the core promoter element from -6 to +22 (AGE3), respectively. The site-directed disruption of either AGE2 or AGE3 decreased CAT expression, and the sequential titration of AGF3 binding by in vivo competition remarkably suppressed HepG2-specific CAT activity. Finally, the heterologous thymidine kinase promoter assay showed that AGE2 and AGE3 synergistically conferred HepG2-specific CAT expression. These results suggest that the synergistic interplay between AGF2 and AGF3 is important for the angiotensinogen promoter activation.
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PMID:Molecular mechanism of transcriptional activation of angiotensinogen gene by proximal promoter. 816 41

Rat microsomal epoxide hydrolase (mEH) is one of the detoxification enzymes and selectively expressed in liver. A 350-bp DNA fragment of the proximal promoter was found to contain information sufficient to express the mEH gene in hepatoma cells, however not in nonhepatoma cells. We identified two cis-acting elements, epoxide hydrolase proximal element 1 (EHP1) and 2 (EHP2), in this promoter region by using transient transfection assays. Each element is a new cell-type-specific transcriptional up-regulator. The cell-type-specific activity of EHP1 correlates to the limited cell distribution of its cognate transacting factor(s). In the case of EHP2, a similar or possibly the same cognate factor(s) binding to EHP2 was detected by DNase I footprinting and gel retardation assays in both hepatoma and nonhepatoma cells. However, EHP2 functions as an up-regulator only in hepatoma cells. Our finding adds repertoire to a battery of cis-regulatory elements that are required for liver-specific transcription.
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PMID:Hepatic transcriptional up-regulator of the rat microsomal epoxide hydrolase gene. 828 38

Polychlorinated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzofuran (TCDF) have been shown to induce transcription of the cytochrome P-450IA1 gene by activating an intracellular receptor protein (the Ah- or dioxin receptor) to bind to specific DNA sequences, termed xenobiotic response elements (XREs). However, the expression and inducibility of the cytochrome P-450IA1 activity exhibit tissue-specific differences. With regard to the TCDF induction response, we have examined three human cell types of endodermal (the hepatoma cell line HepG2), ectodermal (normal keratinocytes), and mesodermal origin (normal fibroblasts). DNase I hypersensitivity analysis of the 5' flank and first intron of the P-450IA1 gene showed that in the nonresponsive fibroblasts the chromatin structure lacked open regions while in the two responsive cell types (keratinocytes and HepG2) several constitutive hypersensitive sites as well as TCDF-induced alterations in the chromatin structure could be detected. This observation might correlate with the fact that the XRE, in either the context of the P-450IA1 gene sequences or in front of a heterologous promoter, was inefficient in directing a TCDF induction response in fibroblasts. In in vitro DNA binding studies, the dioxin receptor was activated to a DNA-binding nuclear form in all three cell types. However, in fibroblast nuclear extracts two novel constitutive protein-XRE complexes were detected. The fibroblast factor(s) were immunochemically distinct from the receptor but exhibited indistinguishable DNA binding specificity. These data are compatible with a model where the P-450IA1 is noninducible in fibroblasts due to the presence of a putative repressor(s) which may compete effectively with the receptor for binding to the response element as indicated by in vitro DNA-binding off-rate experiments.
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PMID:Nonresponsiveness of normal human fibroblasts to dioxin correlates with the presence of a constitutive xenobiotic response element-binding factor. 838 88

Rat CYP1A1 promoter activity was suppressed by the presence of a cis negative regulatory element (NRE) at position -843 to -746 in transiently transfected rat H4IIE and human HepG2 hepatoma cells. Removal of the NRE from the promoter-fusion gene constructs caused an increase in the basal promoter activity of 2-6-fold. Co-transfection of the NRE-containing or non-NRE-containing CYP1A1 promoter-fusion gene constructs with a cloned rat NRE, i.e., pNRE, into HepG2 cells caused a 2-fold or greater reduction in constitutive and induced promoter activities. 2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced expression of the endogenous human CYPA1 was also inhibited by transfection of pNRE into HepG2 cells. Deletion of the sequence from base pairs (bp) -658 to -269 in the NRE-containing construct caused a dramatic decrease of constitutive expression in transiently transfected HepG2 cells, compared with an identical construct that lacked the NRE. Deletion of the sequences between bp -658 and -158 in the CYP1A1 promoter did not affect reporter gene activity, indicating a second site of interaction. At least three different rat liver nuclear proteins bound to the rat NRE, as determined by gel mobility shift and DNase I footprinting assays. A 32-bp sequence within the rat NRE, with significant sequence identity to the 26-bp c-myc, fos/jun-octamer-binding, NRE, was protected from DNAse I cleavage by rat liver nuclear extracts. These data suggested a role for this region in the negative regulation of rat CYP1A1.
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PMID:Rat CYP1A1 negative regulatory element: biological activity and interaction with a protein from liver and hepatoma cells. 839 16

Apolipoprotein A-I (apoA-I) is a major protein component of plasma high-density lipoprotein in all species studied, and plays an important role in cholesterol homeostasis. In an earlier study, we cloned and structurally characterized the chicken apoA-I gene. In this study, the 5'-flanking region of the chicken apoA-I gene was sequenced and functionally characterized. Sequence analysis of the 510-nucleotide 5' upstream region revealed the presence of TATA and CCAAT boxes. In addition, we identified binding sites for several transcription factors such as Sp1, AP1, and NFI.2. When the 5' fragment was ligated into a promoterless CAT vector and transfected into a chicken hepatocarcinoma cell line (LMH), the bacterial chloramphenicol acetyl transferase (CAT) gene was expressed, suggesting transcriptional regulation is associated with this region. Transfection studies with other 5' deletion constructs revealed that the sequence spanning the region -82 to +87 contained the major transcriptional activity. DNase I footprinting, gel retardation, and Southwestern blot analyses showed that the fragment interacts with nuclear proteins.
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PMID:Characterization of the chicken apolipoprotein A-I gene 5'-flanking region. 839 17

The hepatitis B virus nucleocapsid minimal promoter contains sequence elements which are similar to the Sp1 transcription factor binding site consensus sequence. The interaction of these regulatory elements with Sp1 was examined by DNase I footprinting with purified Sp1 protein and DNase I footprinting and gel retardation analysis with nuclear extracts from human cell lines and was examined functionally with transient transfection assays in human hepatoma and Drosophila melanogaster Schneider line-2 cells. DNase I footprinting identified two regions of the nucleocapsid promoter, representing three recognition elements, that bound purified Sp1. Gel retardation analysis with Huh7 nuclear extracts demonstrated that each of the three recognition elements bound the same or similar transcription factor(s) as that recognized by the Sp1 consensus sequence recognition element. The function of the nucleocapsid promoter elements was examined by transient transfection assays in D. melanogaster Schneider line-2 cells by using these binding sites cloned into a minimal promoter element. Each of these regulatory regions transactivated transcription from the minimal promoter element in response to exogenously expressed Sp1. In addition, the second Sp1 site was shown to be an essential element of the nucleocapsid promoter in human hepatoma cells. This demonstrates that the hepatitis B virus nucleocapsid promoter contains three functional Sp1 binding sites which may contribute to the level of transcription from this promoter during viral infection.
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PMID:Characterization of functional Sp1 transcription factor binding sites in the hepatitis B virus nucleocapsid promoter. 843 25

In the rat, the gene (rOAT) encoding ornithine aminotransferase (OAT) is expressed in all cell types examined; however, regulation of rOAT expression is complex and cell-type specific. Various regions of the rOAT 5' flanking domain were cloned upstream from the cat reporter gene, and the expression of these OAT::cat fusions was examined following transfection into rat kidney epithelial cells (NRK-52E), human embryonic kidney cells (293), and rat hepatoma cells (H-4-II-E). Although these experiments suggested the presence of one or more positive regulatory elements between nucleotides -661 and -158, and one or more negative elements upstream from nt -897, none of these putative elements appeared to function in a cell-type-specific manner. The nt sequence of 2531 bp of the rOAT domain flanking the promoter revealed several putative promoter/enhancer elements in positions analogous to the human OAT gene, numerous AGGTCA-like motifs related to the binding sites for the estrogen and thyroid hormone receptors, and multiple motifs resembling a putative regulatory element associated with genes encoding enzymes of the urea cycle. Finally, sensitivity of the 5' end of rOAT to cleavage by DNase I was examined, as DNase-I-hypersensitive sites (DHS) are often found in association with cis-acting regulatory elements. Two DHS were identified; one DHS approximately 140 bp upstream, and the second DHS approximately 300 bp downstream, of the transcription start point (tsp). These data provide the foundation upon which to base future studies aimed at elucidating the molecular mechanisms through which rOAT expression is regulated in a cell-type specific manner.
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PMID:Promoter region of the rat gene encoding ornithine aminotransferase: transcriptional activity, sequence, and DNase-I-hypersensitive sites. 846 71

Recent studies have demonstrated the transacting function of the X gene product of hepatitis B virus. However, little information is available on the regulation of X gene expression. In this report, we first investigate a cellular factor regulating X gene transcription by DNA transfection, using the human hepatoma cell line HuH-7, which is permissive for HBV replication as well as X mRNA transcription. A sequence-specific cellular factor was found to bind to the promoter region upstream of the first ATG (nucleotide [nt] 1248) of the X open reading frame. DNase I footprinting analysis showed the binding sequence of this factor to be situated between nt 1097 and 1119, where an 8-bp palindrome structure resides. S1 nuclease analysis of X gene transcripts demonstrated the binding site to be adjacent to two major start sites (nt 1117 and 1125) of X mRNA. Second, we demonstrate that introduction of a mutation into the binding site gives rise to a loss of the binding with a concomitant shift of the transcription start site of X mRNA beyond the 8-bp palindrome structure, causing it to become more heterogeneous. Thus, the promoter-binding protein appears to be involved in directing the transcription initiation site of the X gene toward the downstream region of the X promoter when X protein is produced from X mRNA.
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PMID:A transcription initiation site for the hepatitis B virus X gene is directed by the promoter-binding protein. 847 61


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