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

In humans, two cDNAs have been isolated encoding beta-galactoside alpha 2,6-sialyltransferase, differing only in part of the 5' untranslated region. Primer extension data show that the two cDNAs are near full-length clones. RNase protection analysis of different cell types showed that the transcript corresponding to the alpha 2,6-sialyltransferase cDNA isolated from a B-cell library resided only in mature B cells. In contrast, the transcript corresponding to the alpha 2,6-sialyltransferase cDNA isolated from a placenta library was found in all cells tested. Our results also indicate the existence of a third alpha 2,6-sialyltransferase transcript in the hepatoma cell line HepG2. Mature B cells were found to express high amounts of alpha 2,6-sialyltransferase mRNA, compared to other cell types tested, as shown by Northern blot analysis. Moreover there was an increased expression of beta-galactoside alpha 2,6-sialyltransferase mRNA in activated B cells compared to resting B cells. In vitro transcription and translation of the cDNAs resulted in a protein of 45 kDa, but the transcripts were translated with different efficiency, suggesting a role for the 5' untranslated region in regulation of translation. We have also made an alpha 2,6-sialyltransferase construct lacking the specific 5' regions of the two cDNAs. A transcript generated from this construct was translated more efficiently in vitro than the two alpha 2,6-sialyltransferase cDNAs.
 ...
PMID:Cell-specific expression of human beta-galactoside alpha 2,6-sialyltransferase transcripts differing in the 5' untranslated region. 847 18

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin induces the microsomal enzyme cytochrome P4501A1 by increasing the transcription rate of the CYP1A1 gene. Induction requires two basic helix-loop-helix proteins, the ligand-binding aromatic hydrocarbon receptor (AhR) and its heterodimerization partner, the AhR nuclear translocator (Arnt). The AhR/Arnt heterodimer induces transcription by binding to dioxin-responsive elements (DREs) within an enhancer upstream of the CYP1A1 gene. The basic regions of AhR and Arnt are crucial for DRE binding. We have mutated these regions in order to analyze the relationship between DRE binding (determined in vitro using an electrophoretic mobility shift assay) and induction of CYP1A1 transcription (determined in vivo by genetic complementation of AhR-defective and Arnt-defective mouse hepatoma cells, using an RNase protection assay to measure mRNA accumulation). Our findings reveal the amino acids in the basic regions of AhR/Arnt that are important for both DRE binding and induction of transcription. This information provides biological background for the interpretation of structural (e.g. crystallographic) studies of the interactions between AhR/Arnt and the DRE. Our findings also indicate that the in vitro behavior of the mutants does not consistently predict their functional activity in vivo. Thus, genetic complementation constitutes an important and stringent test for analyzing the effects of mutations on AhR/Arnt function.
 ...
PMID:DNA binding by the heterodimeric Ah receptor. Relationship to dioxin-induced CYP1A1 transcription in vivo. 862 73

The cytoplasmic iron regulatory protein (IRP) modulates iron homeostasis by binding to iron-responsive elements (IREs) in the transferrin receptor and ferritin mRNAs to coordinately regulate transferrin receptor mRNA stability and ferritin mRNA translational efficiency, respectively. These studies demonstrate that thyroid hormone (T3) can modulate the binding activity of the IRP to an IRE in vitro and in vivo. T3 augmented an iron-induced reduction in IRP binding activity to a ferritin IRE in RNA electrophoretic mobility shift assays using cytoplasmic extracts from human liver hepatoma (HepG2) cells. Hepatic IRP binding to the ferritin IRE also diminished after in vivo administration of T3 with iron to rats. In transient transfection studies using HepG2 cells and a human ferritin IRE-chloramphenicol acetyltransferase (H-IRE-CAT) construct, T3 augmented an iron-induced increase in CAT activity by approximately 45%. RNase protection analysis showed that this increase in CAT activity was not due to a change in the steady state level of CAT mRNA. Nuclear T3-receptors may be necessary for this T3-induced response, because the effect could not be reproduced by the addition of T3 directly to cytoplasmic extracts and was absent in CV-1 cells which lack T3-receptors. We conclude that T3 can functionally regulate the IRE binding activity of the IRP. These observations provide evidence of a novel mechanism for T3 to up-regulate hepatic ferritin expression, which may in part contribute to the elevated serum ferritin levels seen in hyperthyroidism.
 ...
PMID:Thyroid hormone modulates the interaction between iron regulatory proteins and the ferritin mRNA iron-responsive element. 866 26

Relaxation of the trabecular smooth muscle, which is necessary for penile erection, is controlled locally by neurotransmitters and vasoactive agents. The goal of this study was to identify and characterize muscarinic acetylcholine receptor (mAChR) subtypes expressed in cultured human corpus cavernosum smooth muscle cells (HCC SMC). Binding analysis with L-[benzilic-4,4'-3H(N)]quinuclidinyl benzilate ([3H]QNB) demonstrated the expression of specific muscarinic receptor binding sites in HCC SMC. Analysis of total RNA isolated from whole corpus cavernosum tissue and smooth muscle cells, by RNase protection assays, demonstrated the expression of mRNA transcripts for m1, m2, m3, and m4 mAChR subtypes in whole tissue and m2 and m4 subtypes in cultured cells. In situ hybridization with specific m2 and m4 probes further confirmed the expression of m2 and m4 mRNA transcripts in cultured cells. Carbachol (CCh), a nonselective cholinergic agonist, inhibited cAMP synthesis at low concentrations (0.1-1 microM) and stimulated cAMP synthesis at high concentrations (100 microM), in cultured HCC SMC. CCh (100 microM) further augmented forskolin (FSK), isoproterenol (ISO), and prostaglandin E1 (PGE1)-induced cAMP synthesis. These observations suggest that, in vivo, in HCC, ACh may activate m3 mAChR subtypes on endothelial cells or m2 and m4 subtypes on the SMC. Although m2 and m4 are thought to inhibit adenylate cyclase (AC), the augmentation of cAMP synthesis by high concentrations of CCh in SMC suggests an alternative mechanism of coupling to G-proteins that stimulates AC activity. These studies show that HCC tissue expresses different subtypes of mAChR (m1, m2, m3, and m4), whereas cultured HCC SMC express m2 and m4 subtypes. It is suggested that m2 and m4 receptor subtypes may play an important role in maintaining trabecular smooth muscle tone in vivo. The augmentation of FSK-, ISO, and PGE1-induced cAMP synthesis by CCh suggests possible development of a multidrug therapeutic approach to treatment of erectile dysfunction.
 ...
PMID:Expression of functional muscarinic acetylcholine receptor subtypes in human corpus cavernosum and in cultured smooth muscle cells. 872 95

Truncated hepatitis B virus transcripts terminating downstream of a cryptic CAUAAA polyadenylation signal within the HBx open reading frame have previously been identified in tissue samples from two patients with hepatocellular carcinoma (Hilger et al., 1991, J. Virol. 65, 4284-4291). In this study an HBx expression plasmid was systematically deleted in order to elucidate the DNA sequence context which is required for the conversion of the usually inactive CAUAAA motif into a functional polyadenylation signal. Deletions were made progressively on a stretch of viral DNA which, seen on the transcript level, started downstream of the established UAUAAA polyadenylation signal and proceeded to the cryptic CAUAAA motif. The plasmid constructs obtained were used to transfect cells of the HepG2 line. The analysis of newly synthesized RNA via an RNase protection assay revealed termination downstream of the CAUAAA motif following the removal of GU-rich auxiliary sequences downstream of the poly(A) addition site of the UAUAAA signal. Similar results were obtained when an anchored oligo(dT) primer which recognizes selectively truncated RNA was used for the differential, RT/PCR-mediated amplification of 3'-ends. Thus it could be documented in two ways that inactivation or removal of the UAUAAA signal rendered the CAUAAA motif functional as a poly(A) signal. On the basis of the results obtained, we suggest that chromosomally integrated viral DNA on which the TATAAA motif is removed may constitute a template for truncated as well as for virus/cell hybrid transcripts. We also suggest the use of anchored oligo(dT) primers for the rapid identification of truncated transcripts in tissue samples of HCC patients.
 ...
PMID:DNA sequence requirements for the activation of a CATAAA polyadenylation signal within the hepatitis B virus X reading frame: rapid detection of truncated transcripts. 880 79

Hypoxia-inducible factor 1 (HIF-1) is a DNA-binding heterodimeric protein complex originally described in the transcriptional activation of the erythropoietin gene by hypoxia. This protein complex is composed of two subunits, HIF-1alpha and -1beta (aryl hydrocarbon receptor nuclear translocator, ARNT). In this study, we used ARNT-deficient cells, derived from the mouse hepatoma cell line Hepa1c1c7, to further characterize HIF-1 complex formation and its relationship with gene activation by hypoxia and desferrioxamine (Df). Gel shift assays revealed that ARNT is absolutely required for the formation of the HIF-1 DNA-binding complex. Results from RNase protection assays and Northern blots showed that the lack of functional HIF-1 complex completely abrogated the response to hypoxia of vascular endothelial growth factor (VEGF) and the glycolytic enzymes aldolase A (ALDA) and phosphoglycerate kinase 1 (PGK-1), genes known to be upregulated by low oxygen tension. Desferrioxamine induction of VEGF and PGK-1 genes was reduced in the ARNT-deficient cells, but at difference with hypoxia, it was not completely suppressed. These results suggest that Df is able to activate gene transcription through HIF-1-independent mechanisms. Exposure to hypoxia or Df did not induce any changes in HIF-1alpha and -1beta mRNA levels, suggesting that posttranscriptional mechanisms are involved in HIF-1 complex activation.
 ...
PMID:Absolute requirement of aryl hydrocarbon receptor nuclear translocator protein for gene activation by hypoxia. 890 Apr 15

Although high-affinity growth hormone (GH)-binding protein (GHBP) seems to mirror tissue GH receptor (GH-R) status and effects GH kinetics, the physiological importance and ultimate biological role of GHBP remain largely unknown and obscure. Therefore, the aims of this study were, first, to test the hypothesis that different serum concentrations of GHBP may regulate GH-R/GHBP gene transcription and, second, to define a new nonradioactive polymerase chain reaction (PCR) method to quantify GH-R/GHBP mRNA levels which was to compare with the RNase protection assay. Sera from patients with Laron-type dwarfism (n = 10) and adult obese patients (n = 7) containing distinct GH and GHBP concentrations were added to human hepatoma cells (HuH 7) cultured in a hormonally-adapted medium. GH-R/GHBP gene expression was studied 3 h after the addition of the sera. The results of the regulated GH-R/GHBP mRNA levels imply a direct impact of GHBP on GH-R/GHBP gene transcription under these circumstances. In conclusion, we set up a nonradioactive quantitative PCR method which enables the measurement and quantification of GH-R/GHBP mRNA. The results were identical with the data obtained using RNase protection assay. In addition, these results provide evidence that GHBP may have some effect on the regulation of the GH-R/GHBP transcription and that it is more than simply a shed or secreted product with extracellular destinations and functions. Our personal view, therefore, is that GHBP is rather an active player than an erratic extracellular domain of a receptor.
 ...
PMID:Effect of different serum concentrations of growth hormone-binding protein (GHBP) on the regulation of GH receptor/GHBP gene transcription in a human hepatoma cell line. 903 Sep 71

The "long pentraxins" are an emerging family of genes that have conserved in their carboxy-terminal halves a pentraxin domain homologous to the prototypical acute phase protein pentraxins (C-reactive protein and serum amyloid P component) and acquired novel amino-terminal domains. In this report, a genomic fragment of 1371 nucleotides from the human "long pentraxin" gene PTX3 is characterized as a promoter on tumor necrosis factor-alpha (TNFalpha) and interleukin (IL)-1beta exposure in transfected 8387 human fibroblasts by chloramphenicol acetyltransferase and RNase protection assays. In the same cells, the PTX3 promoter does not respond to IL-6 stimulation. Furthermore, IL-1beta and TNFalpha responsiveness is not seen in the Hep 3B hepatoma cell line. The minimal promoter contains one NF-kappaB element which is shown to be necessary for induction and able to bind p50 homodimers and p65 heterodimers but not c-Rel. Mutants in this site lose the ability to bind NF-kappaB proteins and to respond to TNFalpha and IL-1beta in functional assays. Sp1- and AP-1 binding sites lying in proximity to the NF-kappaB site do not seem to play a major role for cytokine responsiveness. Finally, cotransfection experiments with expression vectors validate that the natural promoter contains a functional NF-kappaB site.
 ...
PMID:Characterization of the promoter for the human long pentraxin PTX3. Role of NF-kappaB in tumor necrosis factor-alpha and interleukin-1beta regulation. 907 34

It is now clearly established that alpha-2 adrenergic receptors can be subdivided in three pharmacological subtypes (alpha-2A, alpha-2B and alpha-2C) encoded by distinct genes (alpha 2C10, alpha 2C2 and alpha 2C4, respectively, in humans). Whereas the study of the regulation of the human alpha-2A adrenergic receptor and of the promoter region of the alpha 2C10 gene has being greatly helped by the availability of the colon carcinoma cell line HT29, the study of the other human receptor subtypes has thus far been limited to homologous desensitization/down-regulation in transfected cells, because of the lack of human cellular models constitutively-expressing alpha-2B or alpha-2C adrenergic receptors. Several human cell lines were thus screened, in an attempt to find such models. Radioligand binding studies with [3H]RX821002 and [3H]MK912, reverse transcription-polymerase chain reactions and RNase mapping experiments with pairs of primers and riboprobes specific for each subtype demonstrated that the hepatoma cell line HepG2 and the neuroblastoma cell line SK-N-MC possess alpha-2 adrenergic receptors of the alpha-2C subtype. However, whereas HepG2 expresses exclusively alpha-2C receptors (55 +/- 7 fmol of [3H]MK912 binding sites/mg of protein), SK-N-MC expresses both alpha-2A and alpha-2C subtypes in fairly similar amounts (20 +/- 8 and 23 +/- 3 fmol of [3H]MK912 binding sites/mg of protein, respectively). The study of the inhibition of 3H-labeled antagonist binding by UK14304 demonstrated that a fraction of the receptor population was coupled to pertussis toxin-sensitive G-proteins, which were identified as Gi2 and Gi3 by immunoblotting. The alpha-2 agonist was, moreover, able to decrease forskolin-stimulated cAMP production by 47% in HepG2 and 23% in SK-N-MC, demonstrating that inhibition of adenylyl cyclase is one of the primary mechanisms of signal transduction in both cell lines. HepG2 and SK-N-MC are the first human cell lines unquestionably shown to natively express alpha-2C adrenergic receptors. The discovery of these two models may be useful for future study of the regulation of alpha 2C4 gene expression in cells of different origins and investigation of the reciprocal regulation of alpha-2A and alpha-2C subtype in single cells.
 ...
PMID:HepG2 and SK-N-MC: two human models to study alpha-2 adrenergic receptors of the alpha-2C subtype. 915 9

Hypoxic induction of erythropoietin (Epo) and other oxygen-dependent genes is mediated by the hypoxia-inducible factor-1 (HIF-1), a heterodimeric transactivator consisting of an alpha and a beta subunit. We previously found that the mouse gene encoding HIF-1alpha harbors two alternative first exons (I.1 and I.2), giving rise to two different HIF-1alpha mRNA isoforms. Here, we show by RNase protection analysis that the exon I.1-derived mRNA isoform is differentially expressed in mouse tissues, being highest in kidney, tongue, stomach, and testis, but undetectable in liver, whereas the exon I.2 mRNA isoform is ubiquitously expressed. Sequence and methylation analysis showed that, in contrast to exon I.1, exon I.2 resides within a region showing typical features of a CpG island, known to be associated with the 5' end of housekeeping genes. We identified a 232-bp minimal exon I.2 promoter that strongly induced reporter gene expression in mouse L929 fibroblasts and Hepa1 hepatoma cells. In contrast to L929 cells, the exon I.1 promoter was inactive in Hepa1 cells and hypoxic exposure (1% O2) markedly reduced exon I.2 promoter activity in Hepa1 cells. Prolonged exposure of mice to hypoxia (7.5% O2 for up to 72 hours) also caused a decrease in liver HIF-1alpha mRNA, whereas aldolase mRNA levels increased. These findings might be related to the relatively low Epo levels in the adult liver.
 ...
PMID:Mouse hypoxia-inducible factor-1alpha is encoded by two different mRNA isoforms: expression from a tissue-specific and a housekeeping-type promoter. 955 7


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>