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 purpose of this study was to clarify the mechanism(s) responsible for the transcriptional regulation of the human CYP3A5 gene. It was found that a region from nucleotides -90 to -40 was involved in the transcriptional activity of the CYP3A5 gene by transfection of a series of 5'-truncated promoter-luciferase chimeric genes into human hepatoma HepG2 cells. A gel shift assay using nuclear extracts prepared from HepG2 cells showed that nuclear factor-Y (NF-Y) and specificity protein (Sp) 1 and Sp3 bound to CCAAT box (-78/-68) and a basic transcription element (BTE) (-67/-46) in the CYP3A5 gene. Furthermore, introduction of mutations in the CCAAT box, the BTE, or both elements decreased the transcriptional activity to 10, 21, or 4% of that seen with the intact gene. Thus, we conclude that the transcription of the CYP3A5 gene is cooperatively regulated by NF-Y, Sp1, and Sp3 in HepG2 cells.
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PMID:Cooperative regulation of CYP3A5 gene transcription by NF-Y and Sp family members. 1148 7

Human CYP3A7 and CYP3A4 are expressed in fetal and adult livers, respectively, although the 5'-flanking regions of the two genes show 90% homology. The purpose of this study was to clarify the mechanism(s) responsible for the transcriptional regulation of the CYP3A7 gene in human hepatoma HepG2 cells that showed fetal phenotypes. Transfection studies using a series of the CYP3A7 or CYP3A4 promoter-luciferase chimeric genes identified a nuclear factor kappaB (NF-kappaB)-like element between nucleotides -2326 and -2297 that conferred the transcriptional activation of the CYP3A7 gene. A 1-base pair mismatch within the corresponding region of the CYP3A4 gene was sufficient for a differential enhancer activity. A gel shift assay using nuclear extracts from HepG2 cells showed that Sp1 and Sp3 bound to the NF-kappaB-like element of the CYP3A7 but not CYP3A4 gene. Specific activation of the CYP3A7 promoter by Sp1 and Sp3 was confirmed by a co-transfection of the p3A7NF-kappaB or p3A4NF-kappaB reporter gene with Sp1 or Sp3 expression plasmid into Drosophila cells, which lacked endogenous Sp family. Additionally, introduction of mutations into binding sites for hepatocyte nuclear factor 3beta, upstream stimulatory factor 1, and a basic transcription element in the proximal promoter attenuated luciferase activity to 20% of the level seen with the intact CYP3A7 promoter. Thus, we conclude that the expression of the CYP3A7 gene in HepG2 cells is cooperatively regulated by Sp1, Sp3, hepatocyte nuclear factor 3beta, and upstream stimulatory factor 1.
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PMID:Novel transcriptional regulation of the human CYP3A7 gene by Sp1 and Sp3 through nuclear factor kappa B-like element. 1149 20

Induction of manganese superoxide dismutase (MnSOD) in response to oxidative stress has been well established in animals, tissues, and cell culture. However, the role of the human MnSOD (hMnSOD) promoter in stimulus-dependent activation of transcription is unknown. The hMnSOD promoter lacks both a TATA and a CAAT box but possesses several GC motifs. In a previous study, we showed that the basal promoter contains multiple Sp1 and AP-2 binding sites and that Sp1 is essential for the constitutive expression of the hMnSOD gene. In this study, we identified an Egr-1 binding site in the basal promoter of hMnSOD. We also found that the basal promoter is responsive to 12-O-tetradecanoylphorbol-13-acetate (TPA)-activated hMnSOD transcription in the human hepatocarcinoma cell line HepG2. The contributions of these binding sites and the roles of the transcription factors Egr-1, AP-2, and Sp1 in the activation of hMnSOD transcription by TPA were investigated by site-directed mutation analysis, Western blotting, and overexpression of transcription factors. The results showed that Sp1 plays a positive role for both basal and TPA-activated hMnSOD transcription, whereas overexpression of Egr-1 has a negative role in the basal promoter activity without any effect on TPA-mediated activation of hMnSOD transcription.
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PMID:TPA-activated transcription of the human MnSOD gene: role of transcription factors Sp-1 and Egr-1. 1156 Jul 79

The X-gene product of hepatitis B virus (HBx) has been implicated in hepatitis B virus (HBV)-mediated hepatocellular carcinoma through its ability to induce liver cancer in some transgenic mice and to transactivate a variety of viral and cellular promoters. In this study, we demonstrated that the level of p21(waf1) RNA was decreased in the HBx-expressing cells and this effect was due to the transcriptional repression of the p21(waf1) gene by HBx via a p53-independent pathway. As the Sp1 binding sites of the p21(waf1) promoter were sufficient to confer HBx responsiveness to a previously non-responsive promoter, we suggested that HBx represses the transcription of p21(waf1) by downregulating the activity of Sp1. Because the tumor repressor p21(waf1) protein is a universal inhibitor of cyclin-CDK complexes and DNA replication that induces cell cycle arrest at the G1-S checkpoint, the repression of p21(waf1) by HBx might play an important role in a HBV-mediated pathogenesis.
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PMID:Transcriptional repression of p21(waf1) promoter by hepatitis B virus X protein via a p53-independent pathway. 1157 65

The 5'-flanking region of the mouse Hex gene was examined in order to identify transcription factors regulating its expression in hepatocytes and haematopoietic cells. We have identified two further GC boxes (GC boxes 3 and 4 at nucleotide positions -149 to -140 and -79 to -70, respectively), i.e. in addition to the two previously determined ones (GC boxes 1 and 2 at nucleotide positions -197 to -188 and -176 to -167, respectively). Luciferase reporter assays revealed that all four GC boxes are transcriptionally active in both MH(1)C(1) rat hepatoma and K562 human chronic myelogenous leukemia cells. Electrophoretic mobility shift assays with specific competitors and antibodies showed that members of the Sp family, namely Sp1 and Sp3, bind to these GC boxes. Overexpression of Sp1 and Sp3 in Drosophila SL2 cells stimulated transcription of the Hex gene through interactions with GC boxes 1 to 4, Sp1 being a more potent activator than Sp3. Thus, we conclude that Sp1 and Sp3 stimulate transcription of the Hex gene in both MH(1)C(1) and K562 cells.
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PMID:Sp family members stimulate transcription of the hex gene via interactions with GC boxes. 1172 91

During the pathogenesis of human hepatocellular carcinoma (HCC), the CpG island encompassing the pi-class glutathione S-transferase gene (GSTP1) becomes hypermethylated. Repression of transcription accompanying CpG island hypermethylation has been proposed to be mediated by methyl-CpG binding domain (MBD) proteins. We report here that inhibition of transcription from hypermethylated GSTP1 promoters in Hep3B HCC cells, which fail to express GSTP1 mRNA or GSTP1 polypeptides, appears to be mediated by MBD2. Treatment of Hep3B cells with 5-azadeoxycytidine (5-aza-dC), a methyltransferase inhibitor, activated GSTP1 expression, whereas treatment with trichostatin A, a histone deacetylase inhibitor, had little effect. To more precisely assess the contribution of the pattern of GSTP1 CpG island methylation on GSTP1 mRNA expression, Hep3B cells were treated for 72 h with 5-aza-dC and then subjected to limiting dilution cloning. Bisulfite sequencing was used to map the methylation patterns of the GSTP1 promoter region in GSTP1-expressing and -non-expressing clones. In the clone that expressed GSTP1 mRNA determined by Northern blot analysis and quantitative reverse transcriptase (RT)-PCR, widespread demethylation of at least one GSTP1 allele was evident. Chromatin immunoprecipitation experiments revealed the presence of MBD2, but not Sp1, at the GSTP1 promoter in Hep3B cells. In contrast, Sp1 was detected at the GSTP1 promoter in a GSTP1-expressing Hep3B 5-aza-dC subclone. To test whether MBD2 might be responsible for the inhibition of GSTP1 transcription from hypermethylated GSTP1 promoters, siRNAs were used to reduce MBD2 polypeptide levels in Hep3B cells. SssI-catalyzed methylation of GSTP1 promoter sequences resulted in diminished luciferase reporter activity after transfection into Hep3B cells. However, when hypermethylated GSTP1 promoter sequences were transfected into Hep3B cells that had been treated with siRNA-targeting MBD2 mRNA, no repression of luciferase reporter expression was evident. These findings implicate MBD2 in the repression of GSTP1 expression associated with GSTP1 CpG island hypermethylation in HCC cells.
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PMID:Methyl-CpG binding domain protein 2 represses transcription from hypermethylated pi-class glutathione S-transferase gene promoters in hepatocellular carcinoma cells. 1196 Sep 94

Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) is common and is associated with a more severe liver disease and increased frequency in the development of hepatocellular carcinoma (HCC). Here, we demonstrated that HBV X protein (HBx) and HCV core protein additively repress the universal cyclin-dependent kinase inhibitor p21 gene at the transcription level. The transforming growth factor-beta responsive element and Sp1 site of the p21 promoter were responsible for the effect of HCV core and HBx, respectively. Furthermore, cell growth was additively stimulated by them, suggesting that additive repression of the p21 might be important to understand the cooperative development of HCC by HBV and HCV.
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PMID:Cooperative repression of cyclin-dependent kinase inhibitor p21 gene expression by hepatitis B virus X protein and hepatitis C virus core protein. 1199 40

At least three different promoter regions (1A, 1B, and 1C) are involved in the expression of the human GR gene. Promoters 1B and 1C are found in a 2800 bp region of DNA immediately upstream of the exon 1C transcriptional initiation site. Transcripts containing either exon 1B or 1C are expressed in a wide variety of human tissues and cultured cells. Luciferase reporter constructs were created containing promoter 1B plus 1C (-2738 to +19), promoter 1B (-2738 to -1046) alone, or promoter 1C (-1045 to +19) alone. All three constructs were equally effective in driving luciferase expression in HeLa (human cervical carcinoma) cells. In Jurkat (human T-cell acute lymphoblastic leukemia) cells, constructs containing promoters 1B plus 1C or promoter 1B were equally active, but the promoters 1B plus 1C construct was 35% more active than the promoter 1C construct. However, in HepG2 (human hepatoma) cells, the promoter 1C construct was as effective as promoters 1B plus 1C and more than twice as effective as promoter 1B. Sequences that reside proximal to the exon 1B transcriptional start site included three Sp1 (FP2-FP4) sites. Another site (FP1) contains the sequence TGATAG, which strongly resembles the consensus binding sequence for the GATA family of transcription factors. However, oligonucleotide competition and supershift analysis of FP1 indicates that this site is not a binding site for GATA proteins. These four sites are in addition to three YY1 and one Sp1 sites previously reported in promoter 1B. In HeLa cells, deletion of the three YY1 sites results in only a 30% loss of activity and substantial loss of activity occurs only after deletion of all four Sp1 sites, indicating the critical importance of Sp1 in GR expression in these cells. In contrast, the elimination of the three YY1 sites results in a dramatic decrease in promoter strength in both HepG2 and Jurkat cells (64 and 77%, respectively), while subsequent deletions of promoter elements do not result in substantial changes in promoter activity in these cell lines. This study shows that both promoters 1B and 1C are important for the ubiquitous expression of the human GR gene. Differences in the utilization of these promoters in various cell types are likely a reflection of different promoter availability and/or the levels of specific transcription factors in the cell. This could contribute to tissue-specific expression of GR levels in different cell types.
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PMID:Characterization of promoter 1B in the human glucocorticoid receptor gene. 1203 77

Reln mRNA and protein levels are reduced by approximately 50% in various cortical structures of post-mortem brain from patients diagnosed with schizophrenia or bipolar illness with psychosis. To study mechanisms responsible for this down-regulation, we have analyzed the promoter of the human reelin gene. We show that the reelin promoter directs expression of a reporter construct in multiple human cell types: neuroblastoma cells (SHSY5Y), neuronal precursor cells (NT2), differentiated neurons (hNT) and hepatoma cells (HepG2). Deletion constructs confirmed the presence of multiple elements regulating Reln expression, although the promoter activity is promiscuous, i.e. activity did not correlate with expression of the endogenous gene as reflected in terms of reelin mRNA levels. Co-transfection of the -514 bp human reelin promoter with either Sp1 or Tbr1 demonstrated that these transcription factors activate reporter expression by 6- and 8.5-fold, respectively. Within 400 bp of the RNA start site there are 100 potential CpG targets for DNA methylation. Retinoic acid (RA)-induced differentiation of NT2 cells to hNT neurons was accompanied by increased reelin expression and by the appearance of three DNase I hypersensitive sites 5' to the RNA start site. RA-induced differentiation was also associated with demethylation of the reelin promoter. To test if methylation silenced reelin expression, we methylated the promoter in vitro prior to transfection. In addition, we treated NT2 cells with the methylation inhibitor aza-2'-deoxycytidine and observed a 60-fold increase in reelin mRNA levels. The histone deacetylase inhibitors trichostatin A (TSA) and valproic acid also induced expression of the endogenous reelin promoter, although TSA was considerably more potent. These findings indicate that one determinant responsible for regulating reelin expression is the methylation status of the promoter. Our data also raise the interesting possibility that the down-regulation of reelin expression documented in psychiatric patients might be the consequence of inappropriate promoter hypermethylation.
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PMID:On the epigenetic regulation of the human reelin promoter. 1208 79

We reported previously that the 5'-flanking region (nucleotides -1976 to -1655) of the human haem oxygenase-1 ( hHO-1 ) gene enhances hHO-1 promoter activity in human hepatoma HepG2 cells, but not in HeLa cells [Takahashi, Takahashi, Ito, Nagano, Shibahara and Miura (1999) Biochim. Biophys. Acta 1447, 231-235]. To define more precisely the regulatory elements involved, in the present study we have functionally dissected this region and localized the enhancer to a 50 bp fragment (-1793 to -1744). Site-direct mutagenesis analysis revealed that two regions were responsible for this enhancer activity, i.e. a hepatocyte nuclear factor-4 (HNF-4) homologous region and a GC box motif homologous region. Mutation in either region alone moderately decreased enhancer activity. However, mutations in both regions reduced promoter activity to the basal level. Electrophoretic mobility-shift assays demonstrated that the P5-2 fragment (-1793 to -1744) interacted with at least two nuclear factors, i.e. HNF-4 and Sp1/Sp3. Co-transfection experiments using Drosophila SL2 cells revealed that HNF-4 and Sp1/Sp3 synergistically stimulated the enhancer activity of the P5-2 fragment. These results indicate that co-operation of HNF-4 with Sp1 or Sp3 leads to the activation of hHO-1 gene expression in hepatoma cells.
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PMID:Co-operation of the transcription factor hepatocyte nuclear factor-4 with Sp1 or Sp3 leads to transcriptional activation of the human haem oxygenase-1 gene promoter in a hepatoma cell line. 1213 7


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