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

---

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

DNA isolated from rat liver by intensive deproteinization with chloroform/isoamyl alcohol and phenol contains low molecular weight peptides in a quantity of about 20 micrograms/mg DNA. These peptides show high specific activity in inhibiting transcription in a reconstituted cell-free system with prokaryotic and eukaryotic RNA polymerase. Their level is markedly decreased in DNA prepared from Novikoff hepatoma cells. Moreover the amino acid analysis and the pattern of analytical separation by high performance liquid chromatography (HPLC) show some biochemical differences between DNA-binding peptides extracted from rat liver and Novikoff hepatoma cells. The possibility that carcinogenesis may involve mechanisms which lead to selective removal of some components of the DNA-binding peptides, is discussed.
...
PMID:DNA-binding peptides from rat liver and Novikoff hepatoma cells: quantitative level and possible biochemical differences. 668 24

Anti-La antibodies are frequently found in patients with autoimmune diseases; the antigen was reported to be a 50,000-Da protein (Rinke, J., and Steitz, J. A. (1982) Cell 29, 149-159). Because this protein was associated with many nascent RNA polymerase III transcripts, it was suggested to be an RNA polymerase III transcription factor. The present study was designed to analyze 4.5 I ribonucleoprotein, an RNA polymerase III transcript which contains the La antigen. It was found that the 3'-end 20-30-nucleotide portion was the most protected portion of 4.5 I RNA when 4.5 I ribonucleoprotein was digested with T1 RNase. When U2 RNA (an RNA polymerase II transcript) and 4.5 I RNA were incubated with the S-100 fraction of Novikoff hepatoma cells, the 4.5 I RNA bound La antigen but the U2 RNA did not. When partial and complete T1 RNase digestion fragments of 4.5 I RNA were incubated with the S-100 fraction, the 3'-end fragments bound preferentially to the La antigen. However, the fragments of 4.5 I RNA bound less efficiently to La antigen than whole 4.5 I RNA. These results indicate that the 3'-end of 4.5 I RNA is the La antigen binding site in this molecule and suggest that the overall conformation of RNA aids in the binding of La antigen.
...
PMID:Identification of a La protein binding site in a RNA polymerase III transcript (4.5 I RNA). 686 91

RNA polymerase I was purified to homogeneity from Morris hepatoma 3924A. Purified RNA polymerase I contained a protein kinase activity but comigrated with the polymerase in nondenaturing gels. RNA polymerase II, purified from the same hepatoma, lacked protein kinase activity. Analysis of the subunit composition of the RNA polymerase I showed the presence of eight polypeptides: S1, Mr 190,000; S2, Mr 120,000; S3, Mr 62,000; S4, Mr 42,000; S5, Mr 24,600; S6, Mr 21,000; S7, Mr 19,500; and S8, Mr 17,500. Antibodies prepared against purified polymerase I specifically inhibited RNA synthesis catalyzed by RNA polymerase I. When subunits of the enzyme were covalently linked to diazobenzyloxymethyl paper, complexes between the antibody preparation and S1-S6 were visualized. No immune complexes were formed between RNA polymerase I antibodies and RNA polymerase II subunits. The antibody preparation was able to inhibit both the protein phosphorylation catalyzed by RNA polymerase I and that catalyzed by a nuclear kinase (NII) purified from the same hepatoma. The two polypeptides of the nuclear kinase--Mr 42,000 and 24,600 (identical in size to S4 and S5 of polymerase I)--formed visible complexes with the RNA polymerase I antibodies. Both S4 and S5 of the polymerase contained an ATP binding site, a property associated with protein phosphorylation and also exhibited by the polypeptides of the purified kinase. These data suggest that polypeptides of Mr 42,000 and 24,600 associated with polymerase I are responsible for its kinase activity.
...
PMID:Protein kinase activity of RNA polymerase I purified from a rat hepatoma: probable function of Mr 42,000 and 24,600 polypeptides. 694 6

RNA polymerase II was purified from Morris hepatoma 3924A by a series of ion-exchange and affinity column chromatographic fractionations, followed by sucrose gradient centrifugation in the presence of 0.3 M KC1. Purified RNA polymerase II had a specific activity of greater than 400 nmol of UMP incorporated (30 min)-1 (mg of protein)-1 by using double-stranded DNA as template. The purified enzyme contained five polypeptides (Mr 214 000, 140 000, 33 000, 25 000, and 21 000) that were present in molar quantities and two additional polypeptides (Mr 19 000 and 18 000) that had a combined molar ratio of 1.0. The cyclic AMP independent nuclear protein kinase NII, also purified from hepatoma 3924A, was able to phosphorylate RNA polymerase II polypeptides of Mr 214 000, 140 000, and 21 000. Phosphorylation of the polymerase was accompanied by enhanced transcription of double-stranded DNA, heat-denatured DNA, and poly[d-(A-T)]. The elevation in RNA polymerase activity was dependent upon the presence of hydrolyzable ATP and resulted from an increased number of RNA molecules synthesized in vitro. The average length of RNA chains was not affected by the kinase. Under similar conditions, protein kinase NII also stimulated homologous RNA polymerase I. In contrast to the phosphorylation of polymerase II, modification of polymerase I resulted in an increase in the average size, but not number, of RNA chains synthesized. The specificity of the NII kinase-catalyzed reaction was demonstrated by the inability of another homologous protein kinase, NI, to phosphorylate or activate RNA polymerase II.
...
PMID:Phosphorylation of deoxyribonucleic acid dependent RNA polymerase II by nuclear protein kinase NII: mechanism of enhanced ribonucleic acid synthesis. 711 96

Novikoff hepatoma cells, grown in monolayer cultures, when permeabilized by treatment with lysolecithin, incorporated 3H-UTP at a high rate for 2 hours at 25 degrees. The incorporation was inhibited by initiation inhibitors such as rifampicin AF/013, heparin and aurintricarboxylic acid. About 75% of RNA polymerase II, and 45% of RNA polymerase I activities were inhibited by rifampicin AF/013. In contrast, transcription in isolated nuclei was not inhibited either by rifampicin AF/013 or heparin. The permeabilized cells apparently retain the mechanisms for reinitiation in vitro and may be a useful model for studies on the effects of proteins on gene transcription.
...
PMID:Initiation of transcription in permeabilized Novikoff hepatoma cells. 719 73

Activity levels of DNA-dependent RNA polymerase I (Pol I; ribonucleoside triphosphate: RNA ribonucleotidyl transferase, E.C. 2.7.7.6, eucaryotic type I) have been compared in five transplantable murine hepatomas and livers of three inbred mouse host strains. Three tumors (H6, H4 and H134) contained about 350-450 units of Pol I activity/g of tissue. Two hepatomas (H129 and BW7756) contained about 120-150 units of activity/g of tissue. Livers contained about 100-150 units/g of tissue. Chromatographic comparisons revealed that hepatoma Pol I is slightly less anionic than the liver enzyme. Thermal denaturation studies were carried out using Pol I partially purified from a high-activity line hepatoma (H6), a low-activity line hepatoma (H129) and livers of the appropriate host strains. Pol I from H6 tumors was denatured at 40 degrees C with a half-time of 2 min. The enzyme from H129 tumors and host livers was denaturated with a half-time of 7 min. These data indicate that hepatoma H6 expressed a structural variant of Pol I. This is the first Pol I variant ever reported.
...
PMID:DNA-dependent RNA polymerase I from hepatomas: comparison of activity levels and properties. 724 19

We have recently purified a cyclic nucleotide-independent, heparin-sensitive nuclear protein kinase (NII) from Morris hepatoma 3924A and demonstrated an apparent relationship of this kinase to the two subunits (Mr = 42,000 and 24,600) of RNA polymerase I. When homogeneous protein kinase NII was recombined with purified homologous RNA polymerase I containing limiting quantities of endogenous kinase, RNA synthesis was stimulated as much as 5-fold during a 90-min incubation. The enhanced RNA synthesis was due to an increase in the average RNA chain length; protein kinase did not alter the number of RNA molecules synthesized by the polymerase. Phosphorylation of RNA polymerase occurred at serine and threonine moieties. Unlike the NII kinase, purified homologous NI kinase did not phosphorylate RNA polymerase I and, as a result, did not alter transcription. These data indicate that 1) RNA polymerase I is activated by protein kinase NII, 2) endogenous protein kinase NII remaining with highly purified RNA polymerase I does not fully phosphorylate RNA polymerase I in vitro, and 3) protein kinase NII is capable of regulating RNA polymerase I activity by preventing premature termination of RNA chains.
...
PMID:Activation of purified hepatoma RNA polymerase I by homologous protein kinase NII. 728 32

A nuclear protein kinase, designated NII, was purified essentially to homogeneity from the Morris hepatoma 3924A. In the presence of excess Mg2+, phosphorylation of casein by the kinase was stimulated by spermine (1-5 mM) and was inhibited completely by 0.1 microgram/ml heparin. The apparent Km for casein was reduced in the presence of spermine. Spermine preferentially augmented phosphorylation of threonine residues. The kinase was also associated with highly purified RNA polymerase I and appears to correspond to two polypeptides (Mr 42,000 and 24,600) of the polymerase. RNA polymerase I polypeptides of Mr 120,000 (S2), Mr 65,000 (S3) and Mr 24,600 (S5) were phosphorylated by the endogenous kinase. Spermine enhanced phosphorylation of the RNA polymerase I subunits as much as 20-fold. Phosphorylation activated RNA polymerase I; the phosphorylated enzyme synthesized longer product with no apparent effect on the number of RNA chains initiated.
...
PMID:Spermine-mediated phosphorylation of RNA polymerase I and its effect on transcription. 733 1

The amount and/or activity of DNA-dependent RNA polymerase I, Ii and III from resting liver, regenerating liver and a series of Morris hepatomas (5123D, 7800, 7777, 3924A) were determined after extraction of the enzymes from whole tissue homogenates and subsequent fractionation by DEAE-Sephadex column chromatography. When compared with resting liver, the tumours exhibited a characteristic enzyme pattern in which polymerase I, but not II, was increased. The increase in RNA polymerase I was proportional to the tumour growth rates. Alterations in polymerase III were confined to the most rapidly proliferating hepatomas. By contrast, all classes of RNA polymerase were found to be increased during liver regeneration. Relative to resting liver, the fastest growing tumour, 3924A, exhibited the highest activities and/or amounts of RNA polymerase I (8-fold) and III (5-fold) per g of tissue. These alterations in the tumour RNA polymerases were reflected in corresponding increases in the transcriptionally active (bound or chromatin-associated) enzyme population. The mechanisms underlying the augmented synthesis of RNA in vitro by bound polymerase I from hepatoma 3924A were elucidated by product analysis. The results indicated that, relative to liver RNA polymerase I, the tumour enzyme produced more nascent RNA chains and elongated these chains at a faster rate. The number of 3'-termini, as measured by incorporation into uridine, was higher in the hepatoma even under conditions which prevented re-initiation. suggesting increased amount of transcriptionally active RNA polymerase I in the tumour.
...
PMID:Transcriptionally active RNA polymerases from Morris hepatomas and rat liver. Elucidation of the mechanism for the preferential increase in the tumour RNA polymerase I. 747 79

T7 RNA polymerase transcripts of a putative full-length cDNA clone of hepatitis C virus type 1 (HCV-1) were used to transfect a differentiated human hepatoma cell line, Huh7. The transfected genome replicated in cells, as evidenced by the appearance of progeny HCV RNA, detection of negative-strand viral RNA, and incorporation of [3H]uridine into the viral genome. Incubation of naive Huh7 cells with conditioned medium from transfected cells resulted in a new HCV infection, suggesting the production of biologically active virus in the inoculum. Maintenance of the transfected cells under serum-free culture conditions resulted in the selection of persistently infected cells which displayed a distinctive cellular morphology. This is the first demonstration that HCV RNA produced from cloned HCV cDNA is infectious and replication competent. This approach should provide a valuable system for studying HCV replication, persistence, and pathogenicity.
...
PMID:Transfection of a differentiated human hepatoma cell line (Huh7) with in vitro-transcribed hepatitis C virus (HCV) RNA and establishment of a long-term culture persistently infected with HCV. 798 24


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

---