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 gene for ornithine transcarbamylase (OTC; EC 2.1.3.3), a urea cycle enzyme, is expressed almost exclusively in the liver and small intestine. To identify DNA elements regulating transcription of the OTC gene in the liver, transient expression analysis was carried out by using hepatoma (HepG2) and nonhepatic (CHO) cell lines. The 1.3-kilobase 5'-flanking region of the rat OTC gene directed expression of the fused chloramphenicol acetyltransferase gene in HepG2 cells much more efficiently than in CHO cells. Analysis of deletion mutants of the 5'-flanking region in HepG2 cells revealed that there are at least one negative and two positive regulatory elements within the about 220-base-pair immediate 5'-flanking region. DNase I footprint analysis showed the presence of factors binding to these regulatory elements in nuclear extracts of rat liver and brain, and footprint profiles at the two positive elements exhibited liver-specific features. Transient expression analysis also revealed the existence of an enhancer region located 11 kilobases upstream of the transcription start site. The OTC enhancer was able to activate both its own and heterologous promoters in HepG2 but not in CHO cells. The enhancer was delimited to an about 230-base-pair region, and footprint analysis of this region revealed four protected areas. Footprint profiles at two of the four areas exhibited liver-specific features, and gel shift competition analysis showed that a factor(s) binding to the two liver-specific sites is related to C/EBP. These results suggest that both liver-specific promoter and enhancer elements regulate expression of the OTC gene through interaction with liver-specific factors binding to these elements.
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PMID:Promoter and 11-kilobase upstream enhancer elements responsible for hepatoma cell-specific expression of the rat ornithine transcarbamylase gene. 230 62

We have previously identified a series of five DNase-I hypersensitive (HS) sites within and around the rat phosphoenolpyruvate carboxykinase (PEPCK) gene. The far upstream region has now been sequenced, and the tissue-specific HS site has been mapped more precisely at 4,800 base pairs upstream of the transcription start site of the PEPCK gene. DNA fragments that include the HS site were cloned upstream of various promoters to test whether these regions modulate transcription of the chloramphenicol acetyltransferase reporter gene. Chloramphenicol acetyltransferase activity was enhanced when the DNA fragment encompassing the upstream HS site was linked to various lengths of the PEPCK promoter or to the heterologous simian virus 40 promoter. This upstream region in conjunction with the proximal promoter, which may contain a tissue-specific element, conferred maximum activation in H4IIE hepatoma cells, which express the endogenous PEPCK gene. When these experiments were performed in XC cells, in which the gene is not expressed, transcriptional activation by the upstream element was still significant. Evidence of a specific protein-DNA interaction, using DNA mobility shift and DNase I footprinting assays, was obtained only when using H4IIE cell nuclear extracts. Competition assay showed that the interacting factor may be similar or identical to the liver-specific factor HNF3. We suggest that this protein factor binds to DNA within the HS site and interacts with the proximal promoter region to control tissue-specific high-level expression of the PEPCK gene.
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PMID:Interaction of a liver-specific factor with an enhancer 4.8 kilobases upstream of the phosphoenolpyruvate carboxykinase gene. 235 22

When intact nucleoli were prepared in the presence of enough leupeptin and phenylmethanesulfonyl fluoride to inhibit protease action, electrophoretic patterns of their constituent proteins were reproducible and very similar for L, HeLa, CHO, and rat hepatoma cells. "Core nucleoli", defined as that nucleolar fraction which remains after extensive DNase I action, had a protein composition similar to that of crude intact nucleoli, but were enriched for snRNA U3. Core nucleolar proteins included all of the histones, ribosomal proteins, and phosphorylated proteins with mobilities corresponding to 110 (protein C23) and 160 kilodaltons (kDa). The presence of protein C23 and of lamins A and C in nucleoli and core nucleoli was further verified by reaction with specific antibodies after one- or two-dimensional electrophoresis. A class of higher molecular weight proteins, ranging from 70 to greater than 200 kDa by mobility, was observed. It included at least 25 specific proteins, almost all of them highly acidic (pI less than 3.5). Treatment of core nucleoli with ethylenediaminetetraacetic acid/hypotonic buffer solubilized 30-35% of the small and large molecular weight proteins. In contrast, washing core nucleoli with 2 M NaCl selectively released U3 snRNA, 95% of the ribosomal RNA, and about half of the proteins, including C23 and most of the histones, ribosomal proteins, and other lower molecular weight proteins. The fraction remaining insoluble, "nucleolar matrix", was enriched for proteins of 34 and 57 kDa, lamins A and C, and most higher molecular weight proteins, as well as a portion of ribosomal spacer DNA.
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PMID:Proteins and RNA in mouse L cell core nucleoli and nucleolar matrix. 243 Jun 16

We have examined the chromatin structure of the 5'-flanking region of the albumin and alpha-fetoprotein (Afp) genes in different developing rat tissues and cloned cell lines that display various functional states of these genes. Nuclease-hypersensitive sites were probed with DNase I, using an indirect end-labeling technique. In albumin-producing rat cells two major DNase I-hypersensitive sites were found near the promoter region and one additional site was located approximately 3 kilobases (kb) upstream. Similarly, in Afp-producing rat tissues and cell lines we mapped one DNase I-hypersensitive region close to the promoter region and two cleavage sites further upstream at approximately 2.2 and approximately 3.8 kb from the cap site. The DNase I-hypersensitive sites of both genes were absent in nonhepatic rat cells and therefore appear to be tissue specific. Loss of specific sets of DNase I-hypersensitive sites accompanies the cessation of transcription for the Afp gene in adult rat liver and in a "dedifferentiated" hepatoma cell line. Likewise, specific sets of DNase I-hypersensitive sites disappear during the inactivation of the albumin gene in hepatoma cells. The distal upstream sites of the Afp and albumin genes display the same DNase I sensitivity in expressing and potentially expressible states. These findings suggest that reversible changes in short chromatin regions may be involved in the actual transcription of the albumin and Afp genes, while more permanent tissue-specific changes at other sites correlate with the capacity of these genes to be expressed during hepatic differentiation and neoplasia.
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PMID:Specific sets of DNase I-hypersensitive sites are associated with the potential and overt expression of the rat albumin and alpha-fetoprotein genes. 243 25

We examined DNA methylation and DNase I hypersensitivity of the alpha-fetoprotein (AFP) and albumin gene region in hepatoma cell lines which showed drastic differences in the level of expression of these genes. We assayed for methylation of the CCGG sequences by using the restriction enzyme isoschizomers HpaII and MspI. We found two methylation sites located in the 5' region of the AFP gene and one in exon 1 of the albumin gene for which hypomethylation is correlated with gene expression. Another such site, located about 4,000 base pairs upstream from the AFP gene, seems to be correlated with the tissue specificity of the cells. DNase I-hypersensitive sites were mapped by using the indirect end-labeling technique with cloned genomic DNA probes. Three tissue-specific DNase I-hypersensitive sites were mapped in the 5' flanking region of the AFP gene when this gene was transcribed. Similarly, three tissue-specific DNase I-hypersensitive sites were detected upstream from the albumin gene in producing cell lines. In both cases, the most distal sites were maintained after cessation of gene activity and appear to be correlated with the potential expression of the gene. Interestingly, specific methylation sites are localized in the same DNA region as DNase I hypersensitive sites. This suggests that specific alterations of chromatin structure and changes in methylation pattern occur in specific critical regulatory regions upstream from the albumin and AFP genes in rat hepatoma cell lines.
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PMID:Albumin and alpha-fetoprotein gene transcription in rat hepatoma cell lines is correlated with specific DNA hypomethylation and altered chromatin structure in the 5' region. 243 98

Recently a group of nonhistone proteins with molecular weights ranging from 180-200 K were discovered which are associated with rat hepatoma chromatin specifically (Burkhardt et al., Biochim. Biophys. Acta 781, 165-172, 1984). These hepatoma-associated nonhistone proteins appeared and increased in rats treated with a hepatocarcinogen. Two approaches were used in this study to investigate whether the hepatoma-associated nonhistone chromosomal proteins are present in actively transcribed regions. We found that the limited DNase I digestion of Morris hepatoma 7777 chromatin released antigenic proteins not detected in normal liver chromatin digests. The association of antigenic nonhistone proteins with nuclear matrices was also studied. Using immunoblot analysis of nuclear matrices and total chromatin, the antigenic nonhistone chromosomal proteins were determined. Hepatoma-associated nonhistone protein antigens were extensively concentrated in the nuclear matrices. In the present study, the transcriptionally-active alpha-fetoprotein gene and the nontranscribed beta-globin gene were used as gene markers to determine the transcriptionally active chromatin region. Data presented in this paper indicate that hepatoma-associated NHPs are localized in active chromatin.
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PMID:Hepatoma-associated nonhistone chromosomal proteins are present in active chromatin. 244 95

Mutations were introduced in 7 kilobases of 5'-flanking rat alpha 1-fetoprotein (AFP) genomic DNA, linked to the chloramphenicol acetyltransferase gene. AFP promoter activity and its repression by a glucocorticoid hormone were assessed by stable and transient expression assays. Stable transfection assays were more sensitive and accurate than transient expression assays in a Morris 7777 rat hepatoma recipient (Hepa7.6), selected for its strong AFP repression by dexamethasone. The segment of DNA encompassing a hepatocyte-constitutive chromatin DNase I-hypersensitive site at -3.7 kilobases and a liver developmental stage-specific site at -2.5 kilobases contains interacting enhancer elements sufficient for high AFP promoter activity in Hepa7.6 or HepG2 cells. Deletions and point mutations define an upstream promoter domain of AFP gene activation, operating with at least three distinct promoter-activating elements, PEI at -65 base pairs, PEII at -120 base pairs, and DE at -160 base pairs. PEI and PEII share homologies with albumin promoter sequences, PEII is a near-consensus nuclear factor I recognition sequence, and DE overlaps a glucocorticoid receptor recognition sequence. An element conferring glucocorticoid repression of AFP gene activity is located in the upstream AFP promoter domain. Receptor-binding assays indicate that this element is the glucocorticoid receptor recognition sequence which overlaps with promoter-activating element DE.
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PMID:Enhancer and promoter elements directing activation and glucocorticoid repression of the alpha 1-fetoprotein gene in hepatocytes. 245 90

Albumin and alpha-fetoprotein (AFP), two major serum proteins, are synthesized predominantly in the liver and yolk sac of mammals. In the present paper we report on the developmental expression of the corresponding genes in nonhepatic rat tissues. Significant quantities of mature albumin and AFP mRNAs were revealed in kidney, pancreas, heart, and lung of fetal and/or newborn rats using dot blot and Northern blot assays. Very low levels of these mRNA sequences were also detected in adult kidney and pancreas using sensitive RNA-cDNA solution hybridization assays. In situ hybridization analysis revealed that the albumin and AFP gene transcripts are present in the tubular cells of the 20-day-old fetal kidney. In order to elucidate further the mechanisms governing this expression, we studied the chromatin structure and methylation pattern in the 5'-end of these two genes. A faint band, corresponding to a specific DNase I-hypersensitive site upstream from the albumin gene, was detected in the fetal and neonatal kidney nuclei but not in adult kidney. For both genes, a site CG, demethylation of which is correlated with expression in liver and hepatoma cell lines, is highly methylated in fetal kidney even though AFP and albumin genes are expressed. Taken together, these results show the presence of a cell population in the rat kidney that actively transcribes both the albumin and AFP genes. The expression of these genes may be mediated by mechanisms differing in at least some steps from those exerted in the liver.
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PMID:Albumin and alpha-fetoprotein gene expression in various nonhepatic rat tissues. 245 23

DNase I footprinting and gel mobility shift analysis showed that an HuH-7 hepatoma nuclear protein, termed AFP1, binds specifically to an AT-rich sequence, TGATTAATAATTACA, in domain B of the human alpha-fetoprotein enhancer. No such binding activity was found in HeLa cell nuclei. Transient transfection studies showed that a 54-base-pair region corresponding to the AFP1-binding site could stimulate the simian virus 40 early promoter to express a linked chloramphenicol acetyltransferase gene in an orientation-independent and cell-specific manner. The correlation between the binding of AFP1 and the stimulation of chloramphenicol acetyltransferase gene expression strongly suggests that specific interaction of AFP1 with the AT motif is important for cell-specific transcriptional enhancement. Competition gel mobility shift analysis revealed that similar AT-rich sequences with high affinities to AFP1 were also present in the promoters of the alpha-fetoprotein and albumin genes. These results suggest that AFP1 may function as a common regulatory factor in the transcription of the alpha-fetoprotein and albumin genes.
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PMID:Interaction of a hepatoma-specific nuclear factor with transcription-regulatory sequences of the human alpha-fetoprotein and albumin genes. 246 95

Previous work identified four upstream cis-acting elements required for tissue-specific expression of the alpha-fetoprotein (AFP) gene: three distal enhancers and a promoter. To further define the role of the promoter in regulating AFP gene expression, segments of the region were tested for the ability to direct transcription of a reporter gene in transient expression assay. Experiments showed that the region within 250 base pairs of the start of transcription was sufficient to confer liver-specific transcription. DNase I footprinting and band shift assays indicated that the region between -130 and -100 was recognized by two factors, one of which was highly sequence specific and found only in hepatoma cells. Competition assays suggested that the liver-specific binding activity was HNF-1, previously identified by its binding to other liver-specific promoters. Mutation of the HNF-1 recognition site at -120 resulted in a significant reduction in transcription in transfection assays, suggesting a biological role for HNF-1 in the regulation of AFP expression.
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PMID:Tissue-specific transcription of the mouse alpha-fetoprotein gene promoter is dependent on HNF-1. 247 22


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