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)

The relationship between DNase I-hypersensitive sites (HSs) and transcriptional enhancers of the rat tyrosine aminotransferase (TAT) gene was examined by comparing HSs in and around the TAT gene with the activity of the corresponding DNA sequences in transient transfection assays. In this manner, we identified two HSs as liver-specific enhancers. Of three hepatoma cell lines examined, only one sustained TAT mRNA levels comparable to those of liver. In this cell line, both enhancers were strongly active, and strong hypersensitivity in chromatin over the enhancers was evident. The other two hepatoma cell lines had reduced levels of TAT mRNA and no or altered hypersensitivity over either the enhancers or the promoter. One of these lines carried a negative regulator of the TAT gene, the tissue specific extinguisher Tse-1. This cell line exhibited all HSs characteristic of the strongly active gene except at the promoter; however, one enhancer was inactive even though hypersensitive in chromatin. In a TAT-nonexpressing cell line, inactivity of both enhancers correlated with absence of the respective HSs. We conclude that although hypersensitivity in chromatin necessarily accompanies cell-type-specific enhancer activity, the occurrence of cell-type-specific HSs does not imply that the underlying sequences harbor enhancers active in transient transfection assays.
 ...
PMID:Chromatin structures of the rat tyrosine aminotransferase gene relate to the function of its cis-acting elements. 197 41

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.
 ...
PMID:Mutational studies reveal a complex set of positive and negative control elements within the chicken vitellogenin II promoter. 201 74

To identify the DNA sequences that cis-regulate the expression of the rat liver pyruvate kinase (L-PK) genes, a series of constructs in which the chloramphenicol acetyltransferase reporter genes is driven by various deleted fragments of the 3200 base pairs (bp) upstream of the L-PK gene cap site have been assayed for transient expression after introduction into hepatoma HepG2 cells, rat hepatocytes in primary culture, fibroblast LTK- cells, myogenic C2C12 cells, and CHO cells. Four distinct regulatory domains have been characterized. A proximal promoter region containing a binding site for the hepatocyte nuclear factor 1 (HNF1) which is sufficient to confer liver specificity, even in the presence of a ubiquitous enhancer. A distal promoter region (-96 to -283 bp) containing binding sites for the liver-specific factor A1 (LFA1), the ubiquitous nuclear factor 1 (NF1), the major late transcriptional factor (MLTF), and so far unidentified proteins binding to the L5-PK region which is essential to maximally activate expression of the construct in HepG2 cells. An extinguisher region, located between positions -2082 and -1170 bp, which decreases efficiency of the L-PK promoter in HepG2 cells, but not in hepatocytes in primary culture. Finally, a far upstream region (-2900 to -2500 bp) which seems to correspond to a liver-specific DNase I hypersensitive site and which behaves in HepG2 cells as an activating sequence efficient in the absence of the extinguisher.
 ...
PMID:cis-acting DNA elements regulating expression of the liver pyruvate kinase gene in hepatocytes and hepatoma cells. Evidence for tissue-specific activators and extinguisher. 201 72

Glutathione S-transferase (GST) Ya subunit gene expression is induced in mammalian tissues by two types of chemical agents: (i) planar aromatic compounds (e.g., 3-methylcholanthrene, beta-naphthoflavone, and 2,3,7,8-tetrachlorodibenzo-p- dioxin) and (ii) electrophiles (e.g., trans-4-phenyl-3-buten-2-one and dimethyl fumarate) or compounds easily oxidized to electrophiles (e.g., tert-butylhydroquinone). To study the mechanism of this induction, we have introduced deletions in the 5' flanking region of a mouse GST Ya subunit gene, fused it to the coding sequence for chloramphenicol acetyltransferase (CAT) activity, and transfected the Ya-CAT genes for expression into hepatoma cells. We show that a single cis-regulatory element, between nucleotides -754 and -713 from the start of transcription, is responsible for the induction by both planar aromatic and electrophilic compounds. Using murine hepatoma cell mutants defective in either the Ah-encoded aryl hydrocarbon receptor (BPrc1 mutant) or in cytochrome P1-450 gene (c1 mutant), we show that induction by planar aromatic but not by electrophilic inducers requires a functional Ah receptor and cytochrome P1-450 activity. From this it is concluded that Ya gene activation by planar aromatic compounds involves metabolism of these inducers by the phase I xenobiotic-metabolizing cytochrome P1-450 system into electrophilic compounds, which is consistent with a recently proposed model [Prochaska, H. J. & Talalay, P. (1988) Cancer Res. 48, 4776-4782]. Therefore, the regulatory sequence of the Ya gene should be considered an electrophile-responsive element (EpRE) activated exclusively by inducers containing an electrophilic center. An EpRE-containing 41-bp oligonucleotide ligated at the -187 site of the Ya gene promoter confers upon it an increase in basal activity and xenobiotic inducibility. The basal activity augments with the number of EpRE copies. DNase I protection patterns show the protection of the EpRE domain by a nuclear factor(s) that becomes more abundant upon exposure of Hepa 1c1c7 cells to tert-butylhydroquinone.
 ...
PMID:Xenobiotic-inducible expression of murine glutathione S-transferase Ya subunit gene is controlled by an electrophile-responsive element. 216 52

The human ADH1, ADH2, and ADH3 genes are closely related members of a gene family which are differentially expressed during liver development. To begin examining the mechanism of this tissue-specific and stage-specific expression, the 5'-flanking nucleotide (nt) sequences of the three genes were determined and the transcription start point (tsp) were identified. Sequences of all three genes indicated a high degree of homology (greater than 80% nt sequence identity) from the AUG translation start codon to about nt -780 relative to the tsp. Transient transfection assays of a set of plasmids containing various lengths of ADH 5'-flanking DNA fused to cat were performed in the HepG2 and Hep3B human hepatoma cell lines. The results indicated that the ADH2 promoter-proximal region was transcriptionally active in the absence of upstream sequences. To identify potential cis-acting elements in the ADH2 promoter-proximal region, a DNase I footprinting assay using a rat liver nuclear extract was used. Protection occurred in several locations including one, between nt -51 and -10, which shares homology with known binding sites for a previously identified rat-liver transcription factor called CCAAT/enhancer binding protein (C/EBP). Purified C/EBP was shown by footprint analysis to bind at two distinct sites in the ADH2 promoter located at nt -51 to -31 and -21 to -10. The TATA-box promoter element at nt -30 to -22 was not protected by C/EBP, but was partially protected by a factor in the rat liver nuclear extract. Thus, it is possible that the flanking C/EBP molecules may create a novel binding pocket for TFIID, the TATA-binding general transcription factor for RNA polymerase II. Alternatively, the C/EBP molecules may block access to the TATA box, and stimulate transcription of ADH2 by interacting with some component(s) other than TFIID.
 ...
PMID:Promoters for the human alcohol dehydrogenase genes ADH1, ADH2, and ADH3: interaction of CCAAT/enhancer-binding protein with elements flanking the ADH2 TATA box. 216 44

Human C-reactive protein (CRP) is the major acute phase reactant during inflammation. Regulation of CRP gene expression has been studied in two experimental systems: transgenic mice and human hepatoma cells. In the first system the human CRP gene flanked by approximately 10(4) bases of 5' and 3' sequences is expressed in a liver-specific and inducible manner. The chromatin configuration of the CRP transgene is characterized by the presence of constitutive and inducible liver-specific DNase I-hypersensitive sites. Inducible sites map precisely at the level of the CRP promoter region. In hepatoma cells we analysed the expression of the bacterial chloramphenicol acetyltransferase (CAT) gene driven by various segments of the CRP promoter. This latter approach has led to the identification of promoter elements responsive to interleukin-6 and of hepatocyte-specific nuclear proteins that interact with them.
 ...
PMID:Regulation of the human C-reactive protein gene, a major marker of inflammation and cancer. 217 Aug 8

A 6.3-kbp segment of DNA, upstream of the human thyroid peroxidase gene, and various deletions thereof were linked to a promoterless bacterial chloramphenicol acetyltransferase reporter gene. These constructs were analyzed by transfection and expression in rat FRTL-5 thyroid cells and in human hepatoma HepG2 cells to localize sequences that are important for thyroid cell-specific expression of the thyroid peroxidase gene. A thyroid-specific enhancer element, capable of activating enhancerless simian virus 40 promoter expression in FRTL-5 cells, was localized to a 230-bp region approximately 5.5 kbp upstream of the human thyroid peroxidase gene transcription start site. DNase I footprinting, using nuclear extracts prepared from FRTL-5 cells, revealed three regions within the 230-bp fragment; none of these regions were protected by nuclear extracts from HepG2 cells. Gel mobility shift assays, using double-stranded oligonucleotides corresponding to the three protected regions, further confirmed the existence of factors in FRTL-5 cells, but not HepG2 cells, able to specifically bind to the enhancer sequences. These results suggest the presence of three cis-acting DNA elements in the human thyroid peroxidase gene enhancer that interact with thyroid-specific trans-acting factors.
 ...
PMID:Characterization of a thyroid-specific enhancer located 5.5 kilobase pairs upstream of the human thyroid peroxidase gene. 217 2

The 5'-flanking region of the human gene encoding beta-alcohol dehydrogenase (ADH2) was shown by DNase I footprinting to contain three tandem binding sites for purified glucocorticoid receptor. The three binding sites lie very close together between nucleotide (nt) positions -245 and -171 with respect to the transcription start point. DNase I footprinting using a rat liver nuclear extract indicated a lack of protection of the glucocorticoid receptor binding sites, but protection of a sequence between nt -209 and -191 which partially overlaps the glucocorticoid receptor binding sites I and II. This site has homology with the known binding site for hepatocyte nuclear factor 1 (HNF1). ADH2 promoter DNA fragments containing various lengths of 5'-flanking sequences were fused upstream from the gene encoding chloramphenicol acetyltransferase (cat) and transfected into the HepG2 human hepatoma cell line. The resulting cat expression was subject to induction by dexamethasone in constructions containing ADH2 DNA between nt -272 and -171. This indicates that the glucocorticoid receptor binding sites identified by footprint analysis function as a glucocorticoid response element (GRE) in a liver cell line. Heterologous ADH-cat fusions, in which the ADH2-GRE was fused to the adenovirus major late promoter, exhibited glucocorticoid induction of cat expression in CV-1B cells when cotransfected with a glucocorticoid receptor expression vector. Glucocorticoid regulation in CV-1B was observed when either all three glucocorticoid receptor binding sites (sites 0, I, II) or the two distal sites (sites 0, I) were present. Overall, these results indicate that the ADH2 gene possesses a functional GRE which can potentially regulate expression transcriptionally.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:A hormone response element upstream from the human alcohol dehydrogenase gene ADH2 consists of three tandem glucocorticoid receptor binding sites. 221 Mar 83

We have cloned the promoter for the human third component of complement (C3) gene and have identified sequences involved in its regulation during the acute-phase response. A construct linking 199 bp of the C3 promoter to the firefly luciferase gene was found to be very responsive to interleukin-1 (IL-1) and modestly responsive to interleukin-6 (IL-6) by transfection analysis in the human hepatoma line Hep3B2. Simultaneous treatment with the two cytokines showed a strong synergy between the actions of the two molecules. A 58-bp fragment (-127 to -70 bp) was shown by 5' and 3' deletional mutagenesis to contain cis-acting elements that mediated both the IL-1 response and the IL-1-plus-IL-6 synergistic response of this promoter. When coupled to a heterologous promoter, this fragment enabled the synergistic induction by IL-1 plus IL-6. Sequences homologous to the palindrome ACATTGCACAATCT, which mediates the induction of the IL-6 gene by IL-1 (S. Akira, H. Isshiki, T. Sugita, O. Tanabe, S. Kinoshita, Y. Nishio, T. Nakajima, T. Hirano, and T. Kishimoto, EMBO J. 9:1897-1906, 1990), and the core sequence of the IL-6-responsive element of the rat alpha 2-macroglobulin gene (CTGGGA; M. Hattori, L. J. Abraham, W. Northemann, and G. H. Fey, Proc. Natl. Acad. Sci. USA 87:2364-2368, 1990) are contained within this fragment in immediate juxtaposition and partially overlapping. Site-directed mutagenesis within this homology region drastically reduced the inducibility of the C3 promoter by either cytokine. DNase I footprinting analysis defined a binding site for the transcription factor CCAAT/enhancer-binding protein (C/EBP), which included the IL-1-responsive element-like sequence. No differences were seen between the footprints generated by using extracts from unstimulated and IL-1-stimulated Hep3B2 cells. However, gel retardation analyses revealed two IL-1-specific bands. The data suggest that the induction by IL-1 is mediated by a factor belonging to the family of C/EBP-related proteins.
 ...
PMID:A 58-base-pair region of the human C3 gene confers synergistic inducibility by interleukin-1 and interleukin-6. 224 55

The effects of lycobetaine (LBT) on DNA single strand break and chromatin conformation were examined by in-situ nick translation method. It was found that LBT did not cause DNA single strand break. After 2-h incubation of murine hepatoma cells with 1-50 micrograms/ml LBT in vitro, the chromatin transcription activity was inhibited gradually. This effect was time- and dose-dependent. Actinomycin D produced a similar effect; 10-hydroxycamptothecin not only caused DNA single strand break, but also altered chromatin conformation; homoharringtonine had no marked influence on either. By molecular hybridization technique, it was found that the effect of LBT on individual genes was somewhat different. After 2-h incubation of the cells with LBT, the sensitivities of c-myc, N-ras, and beta 2-microglobulin genes to DNase I were decreased from 75 +/- 6, 66 +/- 4, 70 +/- 8% to 28 +/- 8, 25 +/- 5, 28 +/- 7%, respectively, while that of c-myb and beta-globin genes (8 + 6%, 6 + 5%) did not change obviously.
 ...
PMID:Effects of lycobetaine on chromatin structure and activity of murine hepatoma cells. 228 45


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