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)

Expression and structural organization of tyrosine aminotransferase (TAT) gene in Morris hepatoma cell line 7777 with active and glucocorticoid-inducible TAT gene and in hepatoma 8994, where TAT gene does not function were analysed. No differences in the number of receptor macromolecules, translocation and nuclear binding of hormone-receptor complexes in hormone sensitive (7777) and resistant (8994) cell lines were demonstrated. Dexamethasone increases TAT gene transcription in 7777 cell line but not 8994. Restriction analysis of TAT gene does not reveal any differences either in structural or in regulatory regions. Gel retardation assay with cloned TAT fragment (-400 b.p.) from normal hepatocytes showed identical shift of mobility in 7777 and 8994 cell lines. Moreover, 5'-flanking sequence (-890 b.p.) of TAT gene linked to the bacterial CAT gene is transiently expressed in both cell lines. We have shown that HpaII site (-105 b.p.) of TAT gene is methylated in those cells where TAT gene does not function (thymus, spleen, Zajdela ascites hepatoma) and is demethylated in TAT gene expressing hepatoma 7777 and normal rat hepatocytes. In hepatoma 8994 there are no DNAse I hypersensitive regions, typical to functioning TAT gene from hepatoma 7777 and normal hepatocytes.
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PMID:[Differences in expression and functional organization of the rat tyrosine aminotransferase gene in two lines of Morris hepatoma, 8994 and 7777]. 167 93

Expression of the liver-specific alpha 1-antitrypsin (alpha 1AT) gene is extinguished in hepatoma/fibroblast hybrids. To define the mechanism of extinction, we identified DNA sequences involved in this process by transiently transfecting mutant alpha 1AT promoters into parental and hybrid cells. The wild-type alpha 1AT promoter (-554 to +44 bp) was highly expressed in rat hepatoma cells, but activity was 100-fold less in fibroblasts or cell hybrids. Mutations in this region failed to activate alpha 1AT expression in nonhepatic cells, but mutations in the binding site for liver factor B1 (LF-B1) reduced hepatic-specific expression greater than 100-fold. Furthermore, the hybrid cells failed to express LF-B1-binding activity and mRNA. This suggested that alpha 1AT extinction in hybrids might be an indirect, lack-of-activation phenotype mediated primarily through repression of LF-B1. To test this possibility, we stably transfected an LF-B1 expression cassette into parental and hybrid cells and monitored expression of transfected and endogenous alpha 1AT genes. Surprisingly, although constitutive LF-B1 expression could activate alpha 1AT-CAT transgenes in these cells, it neither prevented nor reversed extinction of the chromosomal alpha 1AT genes. We conclude that although extinction of the LF-B1 trans-activator accompanies alpha 1AT extinction in cell hybrids, it does not play a causal role in this process.
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PMID:Extinction of alpha 1-antitrypsin gene expression in somatic cell hybrids: evidence for multiple controls. 173 21

We have demonstrated that synthetic oligonucleotide representing glucocorticoid responsive element (GRE I) of MMTV inserted into the enhancerless early promoter of SV40 in p delta SVE-CAT expression vector, enhances transient expression of chloramphenicol acetyltransferase gene in HeLa and hepatoma cells cultivated in the presence of dexamethasone. The following changes in the structure of the core sequences (GTTACAAACTGTTCT) of the synthesized GRE eliminated its enhancing ability: i, changes in the left end of the core sequences from GTTACAAAATGTTCT to TCTTCAAACTGTTCT or to TACTCAAACTGTTCT; ii, the increase of gap between TGTTCT and the inverted repeat of this sequence. The above changes did not eliminate specific binding of glucocorticoid receptor to the synthetic oligonucleotides studied.
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PMID:Introduction of the glucocorticoid binding sequences into the expression vector p delta SVE-CAT and its effect on the CAT gene expression in mammalian cells. 179 99

Because the human hepatoma cell line Hep3B produces erythropoietin (Epo) in a regulated fashion, it can be used to investigate the cis-acting regulatory elements of the Epo gene. Comparison of primate and mouse sequences shows strong homology not only in the coding sequence but also within the 5' flanking region, the first intron, and the 3' flanking region. These portions of the Epo gene were inserted 5' and 3' to a reporter gene, human growth hormone (GH). 5A is a 1,192-base pair (bp) HindIII-Xbal fragment that extends from 378 bp 5' to the cap site through the first intron. To obviate the problem of false initiation of translation from the Epo ATG start codon, this site was changed to TAG by site-directed mutagenesis. 3A is a 255-bp Accl-BglII fragment that extends 67 bp upstream from the Epo termination codon and covers most of the 3' noncoding region of homology. The plasmid DNAs were transfected by electroporation into Hep3B cells with RSVCAT as an internal standard to correct for transfection efficiency. One aliquot of cells was exposed to 50 mumol/L CoCl2 or to 1% O2. At the end of the incubations, GH and Epo were measured in the cell media and the cell pellet was assayed for CAT. Production of GH was stimulated 1.7-fold by cobalt or hypoxia. Furthermore, addition of 3A to the GH gene, irrespective of orientation, stimulated GH production 2.6-fold with CoCl2 and 2.3-fold with hypoxia. Stable cell lines were produced by cotransfection of the above constructions, along with the selectable marker pSV-Neo. In two clones, exposure to hypoxia resulted in much more marked (16-fold) induction of GH. Stimulus of both GH and Epo production by hypoxia was partially abrogated by carbon monoxide. These results demonstrate the presence of promoter and enhancer elements within the human Epo gene that are appropriately responsive to hypoxia and cobalt.
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PMID:Regulatory elements of the erythropoietin gene. 198 94

The endogenous chicken vitellogenin II (VTGII) gene is transcribed exclusively in hepatocytes in response to estrogen. We previously identified two estrogen response elements (EREs) upstream of this gene. We now present an analysis of the VTGII promoter activated by these EREs in response to estrogen. Chimeric VTGII-CAT genes were cotransfected into LMH chicken hepatoma cells along with an estrogen receptor expression vector, and transient CAT expression was assayed after culturing the cells in the absence or presence of estrogen. An analysis of constructs bearing deletions downstream of the more proximal ERE indicated that promoter elements relevant to transcription in LMH cells extend to between -113 and -96. The relative importance of sequences within the VTGII promoter was examined by using 10 contiguous linker scanner mutations spanning the region from -117 to -24. Although most of these mutations compromised VTGII promoter function, one dramatically increased expression in LMH cells and also rendered the VTGII promoter capable of being activated by cis-linked EREs in fibroblasts cotransfected with an estrogen receptor expression vector. Gel retardation and DNase I footprinting assays revealed four factor-binding sites within this promoter. We demonstrate that three of these sites bind C/EBP, SP1, and USF (or related factors), respectively; the fourth site binds a factor that we denote TF-V beta. The biological relevance of these findings is suggested by the fact that three of these binding sites map to sites previously shown to be occupied in vivo in response to estrogen.
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PMID:Mutational studies reveal a complex set of positive and negative control elements within the chicken vitellogenin II promoter. 201 74

Vanadate, at concentrations between 0.5 and 2 mM, rapidly decreased the basal level of P-enolpyruvate carboxykinase (GTP) (EC 4.1.1.32) mRNA and blocked the dibutyryl cyclic AMP (Bt2cAMP)-induced increase in enzyme mRNA in both FTO-2B and H4IIE rat hepatoma cells. The concentration of vanadate necessary to inhibit the expression of this gene was similar to that required for the vanadate-mediated activation of the insulin receptor tyrosine kinase. To determine whether vanadate could inhibit PEPCK gene transcription, a series of chimeric genes containing several deletions in the P-enolypyruvate carboxykinase promoter between -550 and -68 was linked to the structural genes for either amino-3-glycosyl phosphotransferase (neo) or chloramphenicol acetyltransferase and introduced into hepatoma cells using three methods: (a) infection with a Moloney murine leukemia virus-based retrovirus, (b) transfection and stable selection for neo expression, or (c) transient expression of chloroamphenicol acetyltransferase. In FTO-2B hepatoma cells infected with retrovirus, vanadate rapidly (within 1 h) inhibited transcription of the PEPCK-neo gene and blocked induction of gene expression caused by the addition of either Bt2cAMP or dexamethasone to the cells. Vanadate was not a general transcription inhibitor since, it like insulin, stimulated the expression of the c-fos gene. Also, the inhibitory effect of vanadate was rapidly reversible in FTO-2B cells since PEPCK gene expression could be stimulated by Bt2cAMP and dexamethasone after removal of vanadate. A series of 5' deletions in the P-enolpyruvate carboxykinase promoter (-550 to +73) was ligated to the structural gene for neo and stably transfected into hepatoma cells. Sequences responsive to vanadate were detected between -109 and -68. This result was confirmed using H4IIE hepatoma cells transiently expressing the PEPCK-CAT gene. The most likely target for vanadate in that region of the P-enolpyruvate carboxykinase promoter is cAMP regulatory element 1 which maps from -91 to -84. A comparison of the inhibitory effects of insulin and vanadate in this system indicated a major difference in the site of action of these two compounds on PEPCK gene transcription.
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PMID:Vanadate inhibits expression of the gene for phosphoenolpyruvate carboxykinase (GTP) in rat hepatoma cells. 216 40

H4IIE rat hepatoma cells were stably transfected with various phosphoenolpyruvate carboxykinase-chloramphenicol acetyltransferase (PEPCK-CAT) expression vectors. The regulation of the transfected genes was qualitatively similar to that of the endogenous PEPCK gene. CAT expression was increased in response to cAMP and dexamethasone and insulin overrode these effects at concentrations known to be effective in suppressing transcription of the endogenous gene. The effect of insulin was dominant, as it is with the endogenous gene. A series of 5',3', and internal deletions of the PEPCK gene promoter were used to show that this insulin response requires at least two separate elements. One insulin-responsive sequence is located between -468 and -402, relative to the transcription initiation site. The other is between -271 and +69.
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PMID:Regulation of phosphoenolpyruvate carboxykinase gene expression by insulin. Use of the stable transfection approach to locate an insulin responsive sequence. 217 98

The sequences preceding the albumin mRNA start site are able to direct efficient transcription only upon introduction into cells expressing the endogenous albumin gene. In transient expression assays, the activity of a reporter gene (CAT) linked to this promoter is 100-fold higher in H4II differentiated hepatoma cells than in H5 dedifferentiated cells which no longer express their albumin gene. This tissue specificity depends on the very proximal promoter region, composed of a CCAAT box, the proximal element and a TATA box. Deletion of the CCAAT box leads to a two- to threefold decrease in activity, deletion of the proximal element (PE) results in loss of activity. The PE is a high-affinity binding site for HNF1/APF, a strictly liver specific trans-acting factor. When the affinity of this factor for PE is decreased by bacterial methylation (PE includes a dam methylase site), by mutation, or by its replacement with the homologous element from the alpha-fetoprotein gene (AFP), the activity of the short promoter (PE plus the TATA box) is abolished. This activity can be rescued in the presence of the more upstream elements: DEII, DEI and the CCAAT box (recognized, respectively, by the NF1/CTF, C/EBP and NFY/ACF factors) which are then absolutely required. Our results suggest that the upstream elements contribute to promoter activity by stabilizing the HNF1-PE complex and not by direct interaction with TFIID or the RNA polymerase. It is probable that these elements, essentially dispensable in already differentiated hepatoma cells, play a crucial role during development or differentiation to activate the promoter in cells that contain a low concentration of HNF1 and/or an HNF1 unable to open inactive chromatin alone.
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PMID:Anatomy of the rat albumin promoter. 218 62

The Retinol-Binding Protein (RBP) is expressed primarily in the liver. The regulatory elements involved in its tissue-specific expression have been identified and mapped to the 5' flanking region of the RBP gene. In this paper heterokaryons and somatic cell-hybrids have been produced and analysed in order to demonstrate that the RBP gene is subject to extinction and to identify the target sequences of this phenomenon. We show here that the gene is extinguished in fusions of hepatoma with a variety of cells of different species and embryonic lineages. The repression is not due to loss of the gene and occurs also when chromosome 10, where the gene is located, is inherited from the expressing parental cell-type. Hybrid clones were transfected with constructs carrying DNA segments of different lengths from the 5' flanking region of the RBP gene fused to a reporter gene. We demonstrate that extinction takes place also on an exogenous RBP-CAT gene, mimicking the phenomenon observed with the endogenous gene in its chromosomal location. Moreover, we identify and map the target sequences of the putative extinguishing function. Our data thus show that extinction of RBP is mediated through the DNA segment that is involved in its tissue-specific expression.
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PMID:Extinction of retinol-binding protein gene expression in somatic cell-hybrids: identification of the target sequences. 225 20

The estrogen response element (ERE) directly linked to a TATA box induces CAT activity in a hormone-dependent manner in Fe 33 cells, the rat hepatoma cell line FTO-2B, stably transfected with the human estrogen receptor (ER). The same promoter construct mediates the stimulation of in vitro transcription. This stimulation is dependent on the presence of the ERE. Induction of transcription in a variety of nuclear extracts derived from mammalian cells is of the same magnitude irrespective of the presence of ER. Similarly, transcription in vitro mediated by B1 vitellogenin 5' flanking sequences in different nuclear extracts is not due to the interaction of the ER with the ERE. Competition analyses with a variety of oligonucleotides reveal that proteins different from the ER, which recognize ERE-like DNA elements, functionally interact with the ERE in vitro. These experiments suggest that ubiquitous proteins related or even identical to the transcription factor USF (MLTF) activate in vitro transcription in an ERE-dependent manner.
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PMID:Transcription factors different from the estrogen receptor stimulate in vitro transcription from promoters containing estrogen response elements. 232 26


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