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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)

Two types of RNA polymerases [EC 2.7.7.6], polymerases A and B, exist in thermophilic bacteria, Thermus thermophilus HB8. Polymerase B is apparently like the core enzyme of polymerase A but is active only when an alternating copolymer of deoxyadenylic and deoxythymidylic acids (poly d(A-T)) or a mixture of homopolymers of deoxyadenylic acid and deoxythymidylic acid (poly dAdT) is used as a template. Polymerase B was further characterized to elucidate its relation to polymerase A and to determine why it is inactive on natural DNA's. 1. Polymerase B did not show pyrophosphate exchange activity. Dinucleoside monophosphates did not activate the RNA-synthesizing activity. The results suggested that polymerase B had no initiation and presumably no elongation activities. 2. Polymerase B had about 6 times greater affinity to DNA than polymerase A. The binding of polymerase B to DNA was, however, reversible. The complex of DNA with polymerase A was stable and the polymerase was not removed from the initial complex even when a large amount of DNA was added. 3. E. coli sigma subunit could not stimulate the activity of polymerase B toward DNA's. 4. Polymerase B could utilize poly d(A-T) and poly dAdT as templates, but could not use Bacillus cereus DNA though the structure is reported to be similar to that of poly d(A-T).
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PMID:Studies on a thermophilic RNA polymerase which is active only on poly d(A-T) and poly dAdT. 17 54

SV40 DNA fragments chemically attached to neutral cellulose powder with a water-soluble carbodiimide have been used to isolate late lytic viral specific RNA from virus infected cells. Exhaustive hybridization to SV40 DNA reveals that virtually all of the isolated RNA molecules contain SV40 specific sequences. Comparison with SV40 cRNA prepared with purified Escherichia coli RNA polymerase and a SV40 DNA I template suggests that the purity of the isolated SV40 specific RNA is very close to 100%. The background level for the nonspecific binding of RNA to a purified cellulose matrix is very low. Retention of nonspecific RNA by SV40 DNA-cellulose is only 1.5% of the viral specific RNA isolated under saturating conditions for the column. Sedimentation in neutral sucrose suggests that the major 16S viral specific RNA has been isolated largely intact.
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PMID:Isolation of viral specific RNA from SV40 infected cells by viral DNA chemically linked to a cellulose matrix. 17 23

DNA-dependent RNA polymerases were extracted from the nuclei of poorly differentiated tumor, Morris hepatoma 3924A, and purified by an initial chromatography on a DEAE-Sephadex column followed by fractionation on phosphocellulose and finally on a second DEAE-Sephadex column. Three major forms of RNA polymerase (IA, IB and II) were resolved chromatographically. Enzymes IA, IB and II eluted from DEAE-Sephadex at 75, 150 and 210 mM (NH4)2SO4, respectively. The specific activities (nmol UMP incorporated mg protein per 15 min) of polymerases IA, IB and II were 40, 43 and 182, respectively. Concurrently, DNA-dependent RNA polymerases were extracted from normal liver and subjected to similar chromatographic procedure. Upon the final DEAE-Sephadex chromatography, enzymes IA, IB and II eluted at 110, 180 and 210 mM (NH4)2SO4, respectively. The recovery of polymerases IA, IB and II after purification was 0.21, 0,28 and 0.42 unit/mg DNA, respectively, for hepatoma enzymes and 0.07, 0.05 and 0.42 unit/mg DNA for the corresponding liver enzymes.
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PMID:RNA polymerases from a rat hepatoma. Partial purification and comparison of properties with corresponding liver enzymes. 17 77

DNA-dependent RNA polymerases (EC 2.7.7.6) were extracted and partially purified form the nuclei of rat ascites hepatoma cells (AH-130) induced by 4-dimethylaminoazobenzene. The patterns of RNA synthesis and the properties of these enzymes were compared with enzymes from the nuclei of rat liver. The specific activity of RNA polymerase in the homogenate from the nuclei of AH-130 cells was the same as normal rat liver nuclei. RNA polymerase was solubilized from the homogenate at high ionic strength and separated into two forms by DEAE-Sephadex column chromatography. Enzymatic characterization showed that these enzymes corresponded to RNA polymerase I and II. RNA polymerase I more effectively transcribed native DNA than denatured DNA at low salt concentration, but at high salt concentration RNA polymerase I effectively transcribed denatured DNA. RNA polymerase II more effectively transcribed denatured DNA. In AH-130 cells the activity of RNA polymerase I was 4 to 5 times higher than RNA polymerase II, and in rat liver the activity of RNA polymerase I was 1.5 to 2 times higher than RNA polymerase II. The activity of RNA polymerase I in AH-130 cells may have increased by induction.
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PMID:A comparative study of DNA-dependent RNA polymerases from rat ascites hepatoma cell nuclei and from rat liver nuclei. 18 Jul 54

Two forms of yeast RNA polymerase A are resolved by phosphocellulose chromatography. One of these, called RNA polymerase A, is lacking two polypeptide chains of 48,000 and 37,000 daltons. The properties of the two enzymes are compared in the present paper. RNA polymerase A transcribes d(A-T)n with a similar efficiency as the complete enzyme, but it is comparatively much less active with native DNA. The two enzymes can also be differentiated on the basis of their ionic strength and divalent cation requirements. RNA polymerase A has a particularly low activity at high salt and low Mg2+ concentrations. Thermal inactivation curves of the two enzymes are different when residual activity is assayed with native DNA. In contrast with d(A-T)n as template the apparent inactivation curves of the two enzymes are identical. The data suggest that the two dissociable polypeptide chains play an important role in transcription. The template specificity of yeast RNA polymerase B was further investigated using SV40 DNA-FI as template. RNA polymerase B is able to retain [3H]SV40 DNA-FI on nitrocellulose filters but the enzyme-DNA complex is very unstable. The observation that RNA polymerase B can transcribe to some extent a supercoiled DNA but not a linear double stranded template supports the hypothesis that the enzyme needs some unpaired DNA structure to initiate transcription.
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PMID:Further characterization of yeast RNA polymerases. Effect of subunits removal. 18 85

Chromatin prepared at various stages of hormone-mediated development of the chick oviduct was investigated for the relative proportions of transcriptionally active (fraction I) and repressed (fraction II) fractions by ECTHAM-cellulose chromatography. During primary stimulation with estrogen, the amount of chromatin DNA in fraction I plotted as a function of time of stimulation showed a bell-shaped profile, similar to the profile obtained earlier for the number of chromatin sites available to RNA polymerase for initiation of RNA synthesis. Chromatin form a transcriptionally inactive system, hen erythrocytes, eluted mainly (98%) as fraction II. The transcriptionally active fraction I of estrogen-stimulated oviduct contained a 4-fold greater RNA polymerase II activity than was found in fraction II. This could be explained by a differential inhibition of RNA polymerase activity in fraction II since enzyme preparations extracted and purified from both chromatin fractions showed equal activities. In support of this finding, fraction I eluted from ECTHAM-cellulose showed a 4-fold greater concentration of rifampicin-resistant RNA chain initiation sites as compared to fraction II. When chromatin from oviduct mince incubated with labeled progesterone and 17 beta-estradiol and was chromatographed on ECTHAM-cellulose, the transcriptionally active fraction also contained a 4-fold greater concentration of bound hormone (per weight DNA) as compared to the repressed fraction.
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PMID:Studies on the structure and function of chick-oviduct chromatin. 2. Biochemical characterization of two chromatin fractions isolated by ECTHAM-cellulose chromatography. 18 91

We have investigated the manner by which progesterone receptors act to induce initiation of RNA synthesis in a cell-free system derived from chick oviduct. A method utilizing rifampicin enabled us to measure the formation of binary initiation complexes between RNA polymerase and chick oviduct chromatin (Tsai, M.-J., Schwartz, R.J., Tsai S.Y., and O'Malley, B.W. (1975) J.Biol. Chem. 250, 5165-5174) and allowed for the quantitative assessment of RNA chain initiation sites, RNA chain propagation rates, and RNA chain size under conditions which prevent secondary chain reinitiations. We have measured the available initiation sites for transcription in oviduct chromatin prepared from chicks withdrawn from all hormone and then restimulated with a secondary injection of progesterone. Within 1/2 hour after administration of progesterone, the number of initiation sites increased from 8,700 sites/pg of chromatin DNA for the control to 15,500 sites. After 1 hour, the concentration of RNA polymerase needed to saturate chromatin binding sites was increased 60% in comparison to control values, while the number of initiation sites increased 160%. This rapid increment in transcriptional activity preceded temporally the induction of synthesis of ovalbumin mRNA. To test directly the effect of progesterone receptor on transcription, in vitro, a reconstituted cell-free system was employed which contained purified cytoplasmic progesterone-receptor complexes, Escherichia coli RNA polymerase, and chromatin prepared from hormonally withdrawn chick oviducts. Purified progesterone-receptor complex stimulated transcription of oviduct chromatin in vitro by promoting an increase of 3,000 to 5,000 additional sites for RNA chain initiation. These data showed that progesterone receptor can directly increase the number of RNA polymerase binding and initiation sites in the chromatin template in the absence of a detectable change in either the rate of RNA chain propagation or the size of the RNA product. The kinetics of progesterone-receptor stimulation of RNA synthesis in chromatin revealed a t1/2 of 15 min for this effect to occur. This value was identical with the optimal time required for binding of receptor to chromatin. The concentration of receptor required for half-maximal stimulation of RNA chain initiation was approximately 5 x 10(-9) M. This value agreed closely with our previously reported estimates of the affinity (Kd approximately 5 x 10(-9)M) of the progesterone-receptor complex for oviduct chromatin. The stimulatory effect of purified progesterone receptor appeared to be relatively specific for oviduct chromatin in comparison to nontarget tissue chromatins or chick DNA. The data presented here show that steroid hormone-receptor complex can directly regulate gene transcription in vitro in a manner which mimics the events observed in vivo in target cells.
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PMID:Progesterone-binding components of chick oviduct. In vitro effects of purified hormone-receptor complexes on the initiation of RNA synthesis in chromatin. 18 91

The MF2 strain, a mouse myeloma derived cell line, was found to continuously produce C-type viral particles when maintained in tissue-culture. These cells when cultured in an ascitic form by injection to Balb/c mice lost this property. The ability to induce syncytia by cocultivation of the MF2 cell with XC-cells was shown to be related to the viral production. A DNA complementary to viral 70 S RNA was synthesized using the viral reverse-transcriptase endogenous activity. The quality of the probe is discussed and the expression of the viral genome among cellular poly A rich RNA varied concomitently to the syncytium inducing ability as evidenced by molecular hybridization experiments.
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PMID:XC-cell fusion induced by murine plasmocytoma cell. III. RNA gene expression correlated to syncytium formation. 18 44

The endogenous RNA polymerase activity of mouse nucleic is enhanced several-fold by the anionic detergent Sarkosyl. The action of Sarkosyl is exerted primarily on the alpha-amanitin sensitive form of the enzyme. This detergent causes the release of nearly all the protein associated with cellular DNA but does not release initiated RNA polymerase. Sarkosyl was also able to activate the RNA polymerase activity from mitotic cells, in which transcription of the highly condensed chromatin is minimal. The use of this anionic detergent has also permitted the extraction of a nucleoprotein complex from Simian Virus 40 (SV40) infected monkey cells. Molecular hybridization experiments have established the viral specificity of the RNA synthesized in vitro by the endogenous polymerase present in this complex.
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PMID:Effect of Sarkosyl on chromatin and viral RNA synthesis. The isolation of SV40 transcription complex. 18 2

The hybridization properties of the herpes simplex virus type 1 (HSV) genome have been analysed. The DNA has a kinetic complexity of 1 X 10(-8). E. cole RNA polymerase was found to initiate synthesis at about 70 sites on the HSV DNA. The in vitro RNA product from this reaction was complementary to about 80% of the HSV genome. The RNA-DNA hybridization rate constant (Kh) was determined using conditions of both RNA excess and DNA excess. Using this rate constant one can analyse the content of HSV sequences in any RNA population.
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PMID:Annealing and hybridization properties of herpes simplex virus type 1 DNA. 18 38


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