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)

We have characterized in the accompanying paper (P. Herbomel, A. Rollier, F. Tronche, M.-O. Ott, M. Yaniv, and M. C. Weiss, Mol. Cell. Biol. 9:4750-4758, 1989) six different elements in the albumin promoter. One of them, the proximal element (PE), is the binding site for a strictly liver specific factor, APF/HNF1. This binding site contains a bacterial DAM DNA methylase methylation target sequence which, when methylated, decreases the affinity of the protein for this element. When the different albumin promoter constructions were prepared in an Escherichia coli deoxyadenosine methylase-negative strain, the respective contributions of the elements to the overall promoter activity were strikingly different. An intact proximal element plus the TATA box gave almost full transcriptional activity in transient transfection experiments and only in differentiated hepatoma cells of line H4II, whereas the distal elements (distal element III [DEIII], the NF1-binding site DEII, and the E/CBP-binding site DEI) had become essentially dispensable. Mutations affecting the CCAAT box showed only a two- to threefold decrease. When PE was methylated, mutated, or replaced by the homologous element from the alpha-fetoprotein gene, activity in the context of the short promoter (PE plus the TATA box) was abolished. However, activity was restored in the presence of the upstream elements, showing that cooperation with factors binding to the CCAAT box and distal elements favors the functional interaction of the liver-specific APF/HNF1 factor with lower-affinity binding sites.
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PMID:The rat albumin promoter: cooperation with upstream elements is required when binding of APF/HNF1 to the proximal element is partially impaired by mutation or bacterial methylation. 268 64

We have identified and characterized two mutually exclusive nuclear proteins that interact with a single crucial element of the albumin promoter. One, albumin proximal factor (APF), is found only in liver or differentiated hepatoma cells and is probably identical to the liver-specific factor named HNF1, alpha 1TFB, or HP1-binding protein. The other, variant albumin proximal factor (vAPF), is present in dedifferentiated hepatoma cells as well as in somatic cell hybrids that show extinction of the expression of liver-specific proteins, including albumin. Reversion to the hepatic phenotype of either a dedifferentiated variant or an extinguished somatic hybrid clone is accompanied by loss of vAPF and reappearance of APF. These two proteins differ in their thermostability and in their molecular weight, while displaying identical sequence specificities. Both proteins interact with a homologous motif present in promoter regions of several other liver-specific genes. In vitro transcription assays, using a rat liver nuclear extract, indicate that the binding of APF to its target sequence is required for albumin transcription. These results suggest that a modification in the primary structure of a transcription factor is correlated with the differentiated state of the hepatic cell.
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PMID:A liver-specific factor essential for albumin transcription differs between differentiated and dedifferentiated rat hepatoma cells. 316 49

The bovine serum albumin (bSA) promoter has been cloned from bovine genomic DNA using the polymerase chain reaction. In common with other albumin promoters, this promoter functions efficiently in the differentiated rat hepatoma cell line H4II and not in the its dedifferentiated derivative, H5. Analysis of 5' deletions of the bSA promoter after transient transfection into H4II has revealed that a short construct containing the HNF1 binding site and TATA box functions efficiently but requires the presence of the more upstream sequences to achieve full activity Footprint analysis of the promoter reveals seven sites of DNA protein interaction extending from -31 to -213. One of these sites, extending from -170 to -236, whose deletion results in a four fold increase in promoter activity. This site has not previously been reported in other albumin promoters and is bound by the C/EBP-like family of proteins.
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PMID:Isolation and functional analysis of the promoter of the bovine serum albumin gene. 754 56

Transcription of hepatocyte-specific genes requires the interaction of their regulatory regions with several nuclear factors. Among them is the hepatocyte nuclear factor 3 (HNF3) family, composed of the HNF3 alpha, HNF3 beta, and HNF3 gamma proteins, which are expressed in the liver and have very similar fork head DNA binding domains. The regulatory regions of numerous hepatocyte-specific genes contain HNF3 binding sites. We examined the role of HNF3 proteins in the liver-specific phenotype by turning off the HNF3 activity in well-differentiated mhAT3F hepatoma cells. Cells were stably transfected with a vector allowing the synthesis of an HNF3 beta fragment consisting of the fork head DNA binding domain without the transactivating amino- and carboxy-terminal domains. The truncated protein was located in the nuclei of cultured hepatoma cells and competed with endogenous HNF3 proteins for binding to cognate DNA sites. Overproduction of this truncated protein, lacking any transactivating activity, induced a dramatic decrease in the expression of liver-specific genes, including those for albumin, transthyretin, transferrin, phosphoenolpyruvate carboxykinase, and aldolase B, whereas the expression of the L-type pyruvate kinase gene, containing no HNF3 binding sites, was unaltered. Neither were the concentrations of various liver-specific transcription factors (HNF3, HNF1, HNF4, and C/EBP alpha) affected. In partial revertants, with a lower ratio of truncated to full-length endogenous HNF3 proteins, previously extinguished genes were re-expressed. Thus, the transactivating domains of HNF3 proteins are needed for the proper expression of a set of liver-specific genes but not for expression of the genes encoding transcription factors found in differentiated hepatocytes.
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PMID:Overproduction of a truncated hepatocyte nuclear factor 3 protein inhibits expression of liver-specific genes in hepatoma cells. 756 96

Tissue-specific expression of insulin-like growth factor binding protein 1 (IGFBP-1) in the liver has been studied using differentiated (H4II and C2Rev7) and dedifferentiated (H5 and C2) rat hepatoma cell lines. Northern blot analysis showed that endogenous IGFBP-1 mRNA was expressed only in the differentiated cell lines. The first 341 base pairs 5' to the transcription initiation site of the human IGFBP-1 gene were inserted upstream of the chloramphenicol acetyltransferase reporter gene (pBP-1(341)). Expression of this gene from the human IGFBP-1 promoter was 10-16 times more efficient in the H4II line than in the other hepatoma cell lines and 40 and approximately 12 times more so than in rat fibroblasts (FR3T3) and a human cervical carcinoma cell line (C33), respectively. Cotransfection of pBP-1(341) and pRSV-HNF1 and/or pRSV-v-HNF1 (eukaryotic expression vectors that drive the synthesis of the liver-enriched trans-acting factor HNF1 or of v-HNF1, a related form) in C33 recipient cells yielded a 6-fold increase in IGFBP-1 promoter activity by HNF1 and a 2-fold increase by v-HNF1. These increases were dependent on the integrity of an HNF1 binding site located 58-74 nucleotides upstream of the cap site. Stimulation of promoter activity by cotransfection of both HNF1 and v-HNF1 fell between these values. Our results indicate that HNF1 is instrumental in human IGFBP-1 promoter activity in vivo and that v-HNF1 modulates this functional role.
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PMID:Liver-specific expression of human insulin-like growth factor binding protein 1: functional role of transcription factor HNF1 in vivo. 767 42

The liver-specificity of insulin-like growth factor binding protein-1 (IGFBP-1) gene promoter activity has been studied by transient transfection in rat hepatoma cell lines, rat fibroblasts and human cervical carcinoma cells, and shown to be dependent on HNF1. Regulation of IGFBP-1 gene expression has also been studied in rat liver by Northern blot and run-on assays during development, specifically during the perinatal period. The results suggest (1) that the increases in mRNA at birth and +1 day post-natally result from increased transcription and (2) that no decrease in transcription activity accompanies the rapid IGFBP-1 mRNA decay during the neonatal period, arguing for post-transcriptional regulation. Support for transcriptional regulation during the neonatal period was obtained from in vitro footprinting experiments and gel shift data. Three trans-acting factors interact with the h-IGFBP-1 promoter between nt -265 and -305. Two of these, Pc and PHS, were expressed throughout development, as well as during adulthood, and interacted with cis-elements spanning nt -295 to -305 and -265 to -285, respectively. The third, Pa, was expressed only when IGFBP-1 gene expression was high, and interacted with cis-elements spanning nt -285 to -295.
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PMID:Characterization of cis-acting elements and transacting factors involved in the tissue-specific and developmental regulation of IGFBP-1 gene expression. 768 17

The influence of hepatocyte nuclear factor 3 (HNF3) on the level of transcriptional activity from the four hepatitis B virus promoters was investigated by transient-transfection analysis in the dedifferentiated hepatoma cell line, HepG2.1. It was found that the large surface antigen promoter and, to a much lesser extent, the nucleocapsid promoter were transactivated in the presence of HNF3. DNase I footprinting analysis demonstrated that purified recombinant HNF3 alpha protects one region of the large surface antigen promoter. Gel retardation analysis showed that a double-stranded oligonucleotide containing this HNF3-binding site formed a specific complex with DNA-binding proteins in the differentiated hepatoma cell lines, Huh7 and HepG2. The complex formed with Huh7 cell extract comigrated with exogenously expressed HNF3 beta in HeLa S3 extracts and was specifically inhibited from forming by the addition of HNF3 beta antiserum. The promoter element which appears to mediate the HNF3 transactivation was functionally mapped by mutational analysis to a region between nucleotides -65 and -54 relative to the transcriptional start site. This regulatory sequence is within the region protected from DNase I digestion by HNF3 alpha and contains 10 of 12 nucleotides homologous to the HNF3-binding-site consensus sequence. A synthetic promoter construct containing this HNF3-binding site was able to mediate transactivation by HNF3 beta. These and previous results suggest that the hepatitis B virus large surface antigen promoter is regulated by at least two liver-enriched transcription factors, HNF1 and HNF3, which together may contribute to the differentiated liver cell type specificity of this promoter.
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PMID:Regulation of transcription from the hepatitis B virus large surface antigen promoter by hepatocyte nuclear factor 3. 774 73

The phosphoenolpyruvate carboxykinase (PEPCK) gene is regulated at the transcriptional level by a variety of effectors in a tissue-specific fashion. In order to study the parameters involved in the tissue-specific hormonal regulation of the PEPCK gene, we have used a transient expression test in well-differentiated rat hepatoma cells as well as in dedifferentiated variants. In this test, the PEPCK promoter is induced by glucocorticoids in well-differentiated FGC4 cells, but not in H5 dedifferentiated variants, in spite of the presence in H5 cells of the glucocorticoid receptor. Study of the PEPCK promoter using electrophoretic mobility shift assays reveals binding sites for the liver-enriched transcription factors HNF1, vHNF1, HNF3, HNF4, and CAAT/enhancer binding protein members. Overexpression of the liver-enriched transcription factors absent in the dedifferentiated variants, such as HNF1 and HNF4, is not sufficient to restore glucocorticoid response of the PEPCK promoter in the variants. Moreover, systematic analysis of the PEPCK promoter reveals that the presence of a region covering a cAMP-responsive element (CRE1 at -80) and a CAAT box is necessary for full response of the PEPCK promoter to glucocorticoids in well-differentiated rat hepatoma cells. In a cotransfection test, overexpression of the regulatory subunit of protein kinase A (PKA), causing sequestering of PKA, abolishes the glucocorticoid response of the promoter in well-differentiated cells. On the other hand, in dedifferentiated variants, overexpression of the catalytic subunit of PKA restores the response to glucocorticoids. The action of PKA on the glucocorticoid response requires the presence of the CRE1 element and is promoter specific because it does not concern nonhepatic promoters such as the long terminal repeats of the mouse mammary tumor virus. These results suggest that the full response of the PEPCK promoter to glucocorticoids requires activation of another signal transduction pathway, the cAMP-mediated pathway.
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PMID:Response of the phosphoenolpyruvate carboxykinase gene to glucocorticoids depends on the integrity of the cAMP pathway. 781 33

The rat tyrosine aminotransferase(TAT) gene promoter (nucleotides -350 to +1; TAT0.35) was able to sustain liver-specific expression both ex vivo in transient transfection (TAT-expressing H411EC3 hepatoma cells vs. TAT non-expressing CCL1.2 fibroblasts) and in in vitro transcription (rat liver vs. spleen crude nuclear extracts). In either case, the index of tissue specificity (6.2 and 6.7 in ex vivo and in vitro experiments, respectively) was close to that obtained with 10 Kb of TAT gene 5'-flanking sequences in transient transfection. Using computer-assisted search of homologies, DNase I footprinting, gel retardation and methylation interference assays, we showed that TAT0.35 sequences spanning nt -156 to -175 and nt -268 to -281 interacted with the liver enriched NF-1Liver (a member of the NF1 gene family) and HNF1 respectively, whereas those encompassing nt -57 to -85 and nt -283 to -288 interacted with the ubiquitous NF-Y and with ubiquitous 'CCAAT'-box binding factor(s), respectively. Competition studies in in vitro transcription carried out with wild type and mutated oligonucleotides, demonstrated that NF-Y cis-elements were crucial for basal TAT promoter activity, both in liver and spleen whereas NF1Liver and HNF1 were only efficient in the liver (supported approximately 60% and 30% of basal TAT0.35 activity respectively). Altogether, these results support the conclusion that TAT0.35 was able to sustain at least part of the liver specificity of TAT gene expression.
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PMID:Expression from the tyrosine aminotransferase promoter (nt -350 to +1) is liver-specific and dependent on the binding of both liver-enriched and ubiquitous trans-acting factors. 791 Dec 35

LFB1/HNF1 is a hepatocyte-enriched trans-activator involved in the regulation of many liver-specific genes. We report the cloning and characterization of a rat genomic DNA fragment containing about 3.5 kb of the LFB1/HNF1 gene 5'-flanking region. This DNA segment is capable of directing the liver-specific expression of a reporter gene in transfection assays. More interestingly, the basal activity of the LFB1/HNF1 promoter in cultured hepatoma cell lines is down-regulated by exogenously added LFB1/HNF1 protein itself. The ability to repress transcription starting from its own promoter requires the integrity of the N-terminal LFB1/HNF1 DNA-binding domain. Contrary to the expectations, in vitro binding experiments failed to demonstrate any specific and functional interaction of purified LFB1/HNF1 with the -3.5 kb promoter sequence. In addition to the DNA-binding domain, a 60 aa region contained in the C-terminus of the protein and distinct from the previously characterized activation domains, is also required for the repressing function.
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PMID:LFB1/HNF1 acts as a repressor of its own transcription. 793 57


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