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)

We have previously described a human complementary DNA that encodes a novel protein which is homologous to members of the steroid/thyroid nuclear receptor multigene family. This novel protein (hap for hepatoma) exhibits strong homology with the human retinoic acid receptor (RAR) which has been recently characterized. To test the possibility that the hap protein might also be a retinoid receptor, a chimaeric receptor was created by replacing the putative DNA binding domain of hap with that of the human oestrogen receptor (ER). The resulting hap-ER chimaera was then tested for its ability to trans-activate an oestrogen-responsive reporter gene (vit-tk-CAT) in the presence of possible receptor ligands. Here we show that retinoic acid (RA) at physiological concentrations is effective in inducing the expression of this reporter gene by the hap-ER chimaeric receptor. This demonstrates the existence of two human retinoic acid receptors designated RAR-alpha and RAR-beta.
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PMID:Identification of a second human retinoic acid receptor. 283 8

cDNAs encoding poly(ADP-ribose) polymerase from a human hepatoma lambda gt11 cDNA library were isolated by immunological screening. One insert of 1.3 kilobases (kb) consistently hybridized on RNA gel blots to an mRNA species of 3.6-3.7 kb, which is consistent with the size of RNA necessary to code for the polymerase protein (116 kDa). This insert was subsequently used in both in vitro hybrid selection and hybrid-arrested translation studies. An mRNA species from HeLa cells of 3.6-3.7 kb was selected that was translated into a 116-kDa protein, which was selectively immunoprecipitated with anti-poly (ADP-ribose) polymerase. To confirm that the 1.3-kb insert from lambda gt11 encodes for poly(ADP-ribose) polymerase, the insert was used to screen a 3- to 4-kb subset of a transformed human fibroblast cDNA library in the Okayama-Berg vector. One of these vectors [pcD-p(ADPR)P; 3.6 kb] was tested in transient transfection experiments in COS cells. This cDNA insert contained the complete coding sequence for polymerase as indicated by the following criteria: A 3-fold increase in in vitro activity was noted in extracts from transfected cells compared to mock or pSV2-CAT transfected cells. A 6-fold increase in polymerase activity in pcD-p(ADPR)P transfected cell extracts compared to controls was observed by "activity gel" analysis on gels of electrophoretically separated proteins at 116 kDa. A 10- to 15-fold increase in newly synthesized polymerase was detected by immunoprecipitation of labeled transfected cell extracts. Using pcD-p(ADPR)P as probe, it was observed that the level of poly(ADP-ribose) polymerase mRNA was elevated at 5 and 7 hr of S phase of the HeLa cell cycle, but was unaltered when artificial DNA strand breaks are introduced in HeLa cells by alkylating agents.
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PMID:Cloning and expression of cDNA for human poly(ADP-ribose) polymerase. 302 72

The human apolipoprotein B (apoB) gene codes for two related proteins, apoB-100 and apoB-48. ApoB-100 is synthesized in the liver, is the major protein constituent of low density lipoprotein, and serves as the ligand for the LDL receptor. cis-acting DNA sequence elements required for hepatic specific apoB transcription were identified in hepatoma (HepG2) and epithelial carcinoma (HeLa) cell lines transfected with apoB/CAT (chloramphenicol acetyltransferase) hybrid constructions. HepG2 cells express the transfected apoB constructions at high levels relative to expression in HeLa cells. Mutational analysis of the 5'-flanking region of the apoB gene revealed the presence of positive and negative regulatory regions. The most distal of these regions, located from -261 to -128 (with respect to the start site of transcription), was found to have a roughly equivalent negative activity in both cell types. However, sequences located from -128 to -86 showed a positive activity in HepG2 cells and a negative activity in HeLa cells. Finally, a sequence element located between positions -86 and -70 was found to have a very strong positive effect in HepG2 cells and only a mild positive effect in HeLa cells. These two proximal regions located between -128 and -70 appear to act together to determine the cell type-specific expression of the apoB gene in HepG2 and HeLa cells. Using the gel mobility shift assay and the DNase I footprinting technique, we demonstrated that DNA binding proteins from HepG2 and mouse liver nuclear extracts interact with the crucial positive region located between -86 and -70. This region was also found to contain sequence elements similar to sequences found in the promoters of other apolipoprotein genes, as well as other genes that are expressed in the liver, suggesting that these genes may share some transcriptional regulatory components.
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PMID:Cell type-specific expression of the human apoB gene is controlled by two cis-acting regulatory regions. 316 76

By transfecting various Xenopus albumin-CAT fusion genes into the mouse hepatoma cell line BW1J a 13 base-pair hepatocyte-specific promoter element (HP1) could be identified. A similar sequence element is also present in the promoter of the albumin and alpha-fetoprotein genes of other vertebrates. Introduction of single point mutations into HP1 destroys its function. Binding studies with nuclear proteins identify a factor interacting with HP1 which is specific for hepatic cells. In-vitro transcription in a rat liver nuclear extract demonstrates that HP1 leads to an increased transcriptional activity. This increased transcription is specifically inhibited by the addition of an HP1-containing oligonucleotide, establishing that the interaction of factors with HP1 is essential for increased transcription. Since HP1 derived from a Xenopus gene functions in mammalian hepatocytes, we conclude that a regulatory system involved in liver-specific gene expression has been conserved during evolution.
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PMID:Hepatocyte-specific promoter element HP1 of the Xenopus albumin gene interacts with transcriptional factors of mammalian hepatocytes. 317 19

Human C-Reactive protein (CRP) is inducible in liver cells during acute inflammation. Around 90 bp from the 5' flanking region of the human CRP gene contain, as shown here, information to induce the expression of a linked bacterial CAT gene specifically in human hepatoma (Hep3B) cells. The promoter is induced rapidly, faithfully and at high efficiency when transfected cells are exposed to conditioned medium from lipopolysaccharide stimulated peripheral monocytes. The sequences required for inducibility are located immediately upstream to the TATA element. A DNA segment from base -121 to -50 is capable of inducing transcription from the heterologous SV40 early promoter. Induction of CRP expression is probably exerted via the binding of at least one positive trans-acting factor.
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PMID:Identification of sequences responsible for acute-phase induction of human C-reactive protein. 337 54

We introduced estrogen responsiveness as a new characteristic into rat hepatoma, mouse Ltk- and human HeLatk-cells by transfecting the human estrogen receptor (ER) cDNA. To measure the estrogen response we used Xenopus vitellogenin gene A2 constructs linked to the bacterial CAT gene. Transient cotransfections of the ER cDNA and the vitellogenin gene-CAT constructs containing the estrogen responsive element (ERE) lead to a hormone dependent induction of CAT activity whereas cotransfected vitellogenin gene constructs lacking the ERE are not inducible. Stable transfections of ER cDNA into Ltk- cells give rise to cell clones that are estrogen responsive as shown by transfection of various vitellogenin gene-CAT constructs. These results prove that the transfected ER is biologically active and is sufficient to make a cell estrogen responsive.
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PMID:Introduction of estrogen-responsiveness into mammalian cell lines. 346 2

The 150-base-pairs region located upstream of the transcriptional start site of the rat albumin gene contains all of the critical sequences necessary for this gene's tissue-specific expression in rat hepatoma cells. In transient expression assays using an improved CAT system or direct mRNA analysis we were able to detect a faithful transcription from the albumin promoter in albumin-negative dedifferentiated H5 hepatoma cells which was 250-fold weaker than in differentiated H4II hepatoma cells producing albumin. This strong tissue specificity could be completely overcome through the cis action of a non-tissue-specific enhancer. Two upstream regions from nucleotides -151 to -119 and from -118 to -94, were required for efficient transcription in H4II cells. Each region contained a sequence motif highly conserved among different species. The effect of the -151/-119 region was strictly tissue specific, while the -118/-94 region was also involved in the low level of transcription observed in H5 cells. Finally, sequences between the CCAAT box and the TATA box also contributed to the overall tissue specificity of rat albumin gene transcription.
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PMID:Determinants of rat albumin promoter tissue specificity analyzed by an improved transient expression system. 347 66

We present, here, evidence that foreign DNA can be specifically delivered to cells by a soluble carrier system that takes advantage of receptor-mediated endocytosis. Our experiments were based on the following concepts: hepatocytes possess a unique receptor that binds and internalizes galactose-terminal (asialo-)glycoproteins; DNA can bind to polycations in a strong but noncovalent manner forming soluble complexes; and the gene for chloramphenicol acetyltransferase, a bacterial enzyme that acetylates chloramphenicol, is not present in mammalian cells. We coupled asialoorosomucoid (ASOR) to poly-L-lysine to form an asialoorosomucoid-poly-L-lysine conjugate. The plasmid, pSV2 CAT, was complexed to the conjugate in a molar ratio of 1:2. To test this complex, a model system was used consisting of hepatoma cell lines, Hep G2, asialoglycoprotein receptor (+), and SK-Hep 1, receptor (-). Each cell line was incubated with filtered ASOR X poly-L-lysine X DNA complex, or controls consisting of DNA plus ASOR, DNA plus poly-L-lysine, or DNA alone. Cells were assayed for the presence of chloramphenicol acetyltransferase activity as a measure of gene transformation. SK-Hep 1, receptor (-) cells, produced no detectable acetylated chloramphenicol derivatives under any condition. However, Hep G2, receptor (+) cells, incubated with the ASOR X poly-L-lysine X DNA complex were transformed as indicated by the presence of chloramphenicol acetyltransferase activity (0.028 chloramphenicol acetyltransferase units/10(6) cells). Mixtures of individual components of the complex failed to transform these cells. Competition by a 10-fold excess of ASOR prevented gene transformation by the ASOR X poly-L-lysine X DNA complex.
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PMID:Receptor-mediated in vitro gene transformation by a soluble DNA carrier system. 355 45

The promoter of the rat alpha-fetoprotein (AFP) gene, which makes the expression of the developmentally regulated AFP gene specific to the liver, is a putative target for transcription factors of the CAAT/enhancer-binding protein (C/EBP), hepatocyte nuclear factor-1 (HNF-1) and nuclear factor-1 (NF-1) families. We have evaluated the influence of these factors on the activity of the AFP promoter by transfection of HepG2 hepatoma cells with the appropriate expression vector plus a CAT plasmid under the control of the AFP promoter. A similar plasmid bearing the rat albumin promoter was used as a control. C/EBP alpha, C/EBP beta and D-binding protein (DBP) acted as trans-activators on the AFP promoter, whereas liver inhibitory protein (LIP), a truncated form of C/EBP beta, was a potent negative regulator of the promoter. C/EBP alpha also bound to and stimulated the activity of the AFP enhancer at -2.5 kb. Interestingly, HNF-1 beta was found to be more potent than HNF-1 alpha in activating the AFP promoter. This effect was specific, as it did not occur with the rat albumin promoter. HNF-1 beta, which is produced earlier than HNF-1 alpha during liver development, would thus have the greater influence on the AFP promoter in early development. Both HNF-1s allowed expression of the AFP promoter in cells of nonhepatic origin. Overexpression of NF-1 induced a specific decrease in the activity of the AFP promoter. This strongly suggests that competition between NF-1 and HNF-1 for binding to their overlapping binding sites on the AFP promoter is critical for modulating its activity. Thus changing combinations of these trans-acting factors may tightly modulate the AFP promoter activity in the course of liver development and carcinogenesis.
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PMID:Members of the CAAT/enhancer-binding protein, hepatocyte nuclear factor-1 and nuclear factor-1 families can differentially modulate the activities of the rat alpha-fetoprotein promoter and enhancer. 751 71

The activity of the insulin-like growth factor binding protein-1 (IGFBP-1) gene promoter was studied in the human endometrial adenocarcinoma cell line HEC-1B. Basal promoter activity was directed by the region +68 to -207 bp, similar to observations in the hepatoma HepG2 cell line. A distal regulatory sequence approximately -2.6 kb from the transcription initiation site strongly enhanced the activity of the IGFBP-1 gene promoter in HEC-1B cells, but not in HepG2 cells. Sequence analysis revealed that this active region resides in 105 bp between -2,628 to -2,732 bp (the Rsa I-Cla I fragment). This region contains many putative active motifs homologous to known cis elements. Additional deletion and mutation in the Rsa I-Cla I fragment showed that the activity was confined to a 58-bp DNA fragment. In cells treated with progestin and co-transfected with progesterone receptor vector hPR1, the CAT activity derived from constructs containing the Rsa I-Cla I fragment was reduced in a dose-dependent manner. The active DNA fragment also stimulated the activity of the heterologous TK/CAT promoter in HEC-1B cells, while the PR complex inhibited this activity by 50%. These observations indicate that most of the regulation of the IGFBP-1 gene in HEC-1B cells is derived from the distal promoter region confined to the Rsa I-Cla I fragment and that the same region mediates an inhibitory effect from the progesterone receptor.
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PMID:Identification of a distal regulatory sequence of the human IGFBP-1 gene promoter and regulation by the progesterone receptor in a human endometrial adenocarcinoma cell line. 752 Jul 2


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