Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An in vitro transcription system was developed from H411EC3 (H4) hepatoma cells, which mimics the in vivo up-regulation by glucocorticoid hormones on ribosomal RNA (rRNA) synthesis. Ribosomal DNA (rDNA) transcription in extracts derived from H4 cells grown in the presence of 100 nM triamcinolone acetonide was 4- to 5-fold greater than that in extracts derived from cells grown in the absence of glucocorticoid. This effect was not a general stimulation by the steroid, as RNA polymerase II transcription of the metallothionein-1 gene which lacked a glucocorticoid responsive element was unaffected. The increased transcription in hormone-treated extracts was also independent of differential ribonuclease activities or inhibitors as ascertained by the inclusion of ribonuclease inhibitor and mixing experiments, respectively. Chromatography of H4 cell extracts on heparin-sepharose followed by transcription complementation analysis, showed that the hormone-induced stimulatory activity eluted with the fraction (TFIA) which contains RNA polymerase I (Pol I). Immunoblot analysis with specific anti-Pol I antibody showed similar subunit profiles in the absence and presence of the hormone. The presence of a Pol I enhancer element in addition to the rDNA promoter did not further modify the glucocorticoid-induced transcription. These results indicate that the glucocorticoid-mediated effects could be observed in cell extracts which accurately initiate transcription of cloned rat rDNA. Moreover, the alterations of rDNA transcription by the hormone is effected by a factor which elutes with fraction TFIA.
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PMID:Glucocorticoid-induced stimulation of ribosomal gene transcription in rat hepatoma cells is mediated by modification of RNA polymerase I or an associated factor. 260 60

Eight eukaryotic promoters have been tested for their activity in vivo in Escherichia coli. The rat beta-actin, rat amylase, rat chymotrypsin B, mouse metallothionein I, rat insulin I, human insulin, Rous sarcoma virus long terminal repeat (RSV LTR) and hepatitis B viral precore promoter activities were measured by using the bacterial chloramphenicol acetyltransferase coding sequences as the reporter function and by primer extension RNA analysis. All eight promoter-chloramphenicol acetyltransferase constructs produce chloramphenicol acetyltransferase activity with the following relative strengths: RSV LTR greater than rat beta-actin greater than rat insulin I greater than rat amylase greater than hepatitis B virus precore greater than human insulin greater than rat chymotrypsin B greater than mouse metallothionein I. A primer extension analysis indicates that transcription from the RSV LTR, rat insulin I, and rat beta-actin promoters initiates at the sites expected for eukaryotic rather than prokaryotic promoters. Thus the site of initiation is determined by the DNA sequence rather than by the RNA polymerase.
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PMID:Eukaryotic promoters drive gene expression in Escherichia coli. 268 Nov 82

We describe a cell-free system in which the transcription of the yeast metallothionein gene is inducible by the addition of metal ions plus a specific regulatory protein. Efficient transcription requires the complete yeast ACE1 metalloregulatory protein, including both its DNA-binding and transactivation domains; a mouse nuclear extract providing RNA polymerase and general transcription factors; a template containing the ACE1 binding site; and Cu(I). Because the binding of ACE1 to DNA is dependent on Cu, it is possible to inhibit transcription by the use of Cu-complexing agents such as CN-. We have used this specific inhibition to show that the ACE1 regulatory protein is required for the maintenance as well as the formation of a functional preinitiation complex. The ability to reversibly induce yeast metallothionein gene transcription in vitro provides a powerful system for determining the molecular mechanism of a simple eukaryotic regulatory circuit.
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PMID:Copper and the ACE1 regulatory protein reversibly induce yeast metallothionein gene transcription in a mouse extract. 268 50

Here we describe a novel expression system for mammalian cells which is based on transcription of hybrid genes containing T7 phage promoters by a T7 phage RNA polymerase targeted to the nucleus of the host cells. The RNA polymerase gene of T7 phage has been modified by substituting a sequence encoding the nuclear location signal of SV40 large T antigen for the N-terminal part of the polymerase gene. Expression of the modified gene is driven by the mouse metallothionein promoter in transfected mouse Ltk- cells resulting in high concentration of the polymerase in the nucleus. Nuclear T7 RNA polymerase directs efficient transcription of the cat gene under control of a T7 promoter. T7 constructs are expressed at a level at least 6 fold higher than the prototype pRSVcat. The unique properties of this heterologeous expression system are discussed.
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PMID:High level gene expression in mammalian cells by a nuclear T7-phase RNA polymerase. 268 45

The requirement for ATP hydrolysis in the initiation of RNA polymerase II (Pol II)-directed transcription and the relationship between ATP and novobiocin action led us to investigate whether novobiocin could inhibit transcription of the mouse metallothionein-I (MT-I) gene. Novobiocin inhibited the MT-I gene transcription in a fractionated rat hepatoma nuclear extract in a dose-dependent manner by direct interaction with a nuclear factor(s). This interaction prevented formation of stable preinitiation complexes but did not affect elongation of MT-I mRNA. Preincubation of the nuclear extract with ATP prevented the action of novobiocin on MT-I gene transcription. Although novobiocin is known to inhibit DNA topoisomerase II, VM-26, a specific inhibitor of this enzyme had no effect on the transcription. These results indicate that novobiocin blocks the Pol II-directed transcription by inhibiting formation of preinitiation complexes at an ATP-dependent step.
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PMID:Novobiocin inhibits initiation of RNA polymerase II-directed transcription of the mouse metallothionein-I gene independent of its effect on DNA topoisomerase II. 282 31

This report summarizes our studies, in context with the results of other laboratories, of the molecular mechanisms of glucocorticoid hormone action. The receptors for these steroids are comprised of single polypeptide chains of about 90,000 molecular weight. Binding of agonist steroids to the receptor induces a conformational change to an active receptor form that is followed by a second change in the glucocorticoid-receptor complex, termed activation, that alters the charge of the complex and results in its binding to specific sites on the DNA termed glucocorticoid regulatory elements (GREs). The GRE on the human metallothionein-IIA gene is located in the 5'-flanking DNA. It can function independently of the gene's promoter, and when ligated upstream from the herpes simplex virus (HSV) thymidine kinase (TK) gene promoter, can activate it. The binding of the glucocorticoid-receptor complex to the GRE probably alters chromatin structure over a limited span to facilitate RNA polymerase action. The regulation by glucocorticoids of growth hormone gene expression is more complex. The steroid appears to elicit both transcriptional and posttranscriptional influences that are also affected by thyroid hormone. Also the glucocorticoid influences appear to be exerted in part through DNA structures located downstream from the transcriptional initiation site. A GRE has been defined in intron A of the hGH gene through gene transfer and DNA binding experiments. Finally, gene transfer experiments suggest that pituitary-specific factors influence the ability of glucocorticoids to affect GH gene expression.
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PMID:Mechanisms of glucocorticoid hormone action. 301 84

As shown by Southern blot analysis, the metallothionein-1 (MT-1) genes in rats comprise a multigene family. We present the sequence of the MT-1 structural gene and compare its features with other metallothionein genes. Three MT-1 pseudogenes which we sequenced apparently arose by reverse transcription of processed mRNA transcripts. Two of these, MT-1 psi a and MT-1 psi c, are retrogenes which derive from the MT-1 mRNA, having diverged from the MT-1 gene 6.9 and 2.6 million years ago, respectively. The third, MT-1 psi b, differs from the MT-1 cDNA by only three nucleotide alterations. Surprisingly, MT-1 psi b also preserves sequence homology for 142 base pairs 5' to the transcription initiation site of the parent gene; it contains a promoter sequence sufficient for specifying metal ion induction. We identified, by S1 nuclease mapping, an RNA polymerase II initiation site 432 base pairs 5' of the MT-1 transcription initiation site of the MT-1 structural gene which could explain the formation of the mRNA precursor to this pseudogene. We were unable to detect MT-1 psi b transcripts, either in liver tissue or after transfection. We conclude that the absence of detectable transcripts from this pseudogene is due to either a reduced level of transcription or the formation of unstable transcripts as a consequence of the lack of a consensus sequence normally found 3' of transcription termination in the MT-1 structural gene.
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PMID:Rat metallothionein-1 structural gene and three pseudogenes, one of which contains 5'-regulatory sequences. 302 30

Metallothioneins that bind copper and zinc have an Mr of 6500 daltons, consist of a single polypeptide chain of 61 amino acids, 25-30 percent of whose residues are cysteine, have a metal-binding capacity of between 5 and 7 g atoms/mol, and contain no disulfide bonds or aromatic amino acids. Zincthionein has been postulated to participate in the transport and storage of zinc, which is involved in more than 235 metalloenzymes, including thymidine kinase, RNA polymerase, and ribonuclease, which in turn play crucial roles in the replication and transcription of DNA during cell division. In addition, trace elements including zinc modulate immune response and function. Conversely, zinc deficiency state causes, for example, thymic atrophy and lymphopenia and modifies antibody-mediated responses to both T-cell-dependent and T-cell-independent antigens. The concentrations of copper, zinc, and metallothionein and the copper/zinc ratio are modified in a number of malignancies. For example, the levels of metallothionein in normal and in malignant human livers are 471 and 75 micrograms/g, respectively. In addition, the copper/zinc ratio is significantly increased in human pancreatic cancer from 1.40 to 2.70. Furthermore, studies involving 64Cu in tumor-bearing mice showed that the distribution of 64Cu was altered and that all tumors contained a relatively high level of 64Cu. Moreover, the activity of superoxide dismutase to remove free oxygen radicals is lower in malignant tissues. Finally, the results of clinical studies suggest that the monitoring of the serum copper/zinc ratio may be a valuable tool, not only in determining the extent of malignancies, but also in predicting the efficacy of treatments.
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PMID:The status of zinc, copper, and metallothionein in cancer patients. 328 43

Nuclear extract from Morris hepatoma 3924A was fractionated by DEAE-Sephadex chromatography. The fraction eluting with 300 mM (NH4)2SO4 (DE-C) was used for transcribing cloned mouse metallothionein-I (MT-I) gene in a run-off assay. This fraction contained the majority of RNA polymerase II as well as the transcription factor(s). Accuracy of MT-I DNA transcription was confirmed by S1 nuclease mapping. Low concentrations (1 microgram/ml) of alpha-amanitin inhibited the reaction, indicating that RNA polymerase II directed the transcription. Unfractionated nuclear extracts from the hepatoma or a rat mammary adenocarcinoma as well as whole cell extract obtained from the mammary tumor also transcribed MT-I gene. The extent of transcriptional activity was in the following order: hepatoma nuclear fraction DE-C greater than whole cell extract derived from rat mammary adenocarcinoma cells greater than nuclear extract derived from rat hepatoma or rat mammary adenocarcinoma cells. These studies have demonstrated that a fractionated nuclear extract obtained from a tissue supports efficient and accurate RNA polymerase II-mediated transcription of MT-I DNA.
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PMID:Accurate transcription of mouse metallothionein-I gene in a fractionated nuclear extract from a rat hepatoma. 355

A hybridoma secreting monoclonal antibodies against RNA polymerase I was produced by the fusion of myeloma cells with spleen cells from a nonimmunized MRL/lpr mouse which is known to produce autoantibodies to RNA polymerase I. The antibodies (McAb-2D11) belong to the IgG2b subclass, reacted specifically with the second largest (120 kDa) subunit of RNA polymerase I, and inhibited accurate transcription of cloned rat rDNA in a fractionated cell extract following immunoprecipitation of RNA polymerase I. McAb-2D11 did not inhibit RNA polymerase II-mediated transcription of the mouse metallothionein-I gene. Immunocytochemical procedures with biotinylated second antibody demonstrated specific immunolocalization of RNA polymerase I in the nucleus. These studies have (a) presented direct evidence that autoantibodies to functional RNA polymerase I are produced in a murine model of systemic lupus erythematosus, (b) demonstrated specificity of the monoclonal antibody for RNA polymerase I, and (c) provided a useful tool for the purification of RNA polymerase I and/or transcription factor(s) associated with RNA polymerase I.
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PMID:Production of monoclonal antibodies against RNA polymerase I from nonimmunized autoimmune MRL/lpr mice and their use in rDNA transcription analysis. 362 76


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