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, complementary to chicken globin mRNA was synthesized using either Avian Myeloblastosis virus reverse transcriptase, or E. coli DNA polymerase I. Transcriptase cDNA sediments at 9 S on sucrose gradients, and is 620 nucleotides in length, representing a complete copy of globin mRNA template. In contrast, Polymerase I cDNA sediments at 4 S, is 100 to 200 nucleotides in length, and is a copy of a small region at the 3'(poly A) end of globin mRNA. Similarly, Transcriptase cDNA and Polymerase I cDNA hybridize to globin mRNA template with characteristic, individual Crot1/2 values. The Crot1/2 value for Transcriptase cDNA hybridization is 7 X 10(-4) mol s 1(-1), and that for Polymerase I cDNA is 5 X 10(-3). This work shows that Avian Myeloblastosis virus reverse transcriptase can use Polymerase I cDNA to prime further cDNA synthesis along the mRNA template. The product of extended cDNA synthesis is identical in length and hybridization properties to oligo (dT) primed transcriptase cDNA.
...
PMID:Gene specific priming of complementary DNA synthesis. 6 22

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).
...
PMID:Studies on a thermophilic RNA polymerase which is active only on poly d(A-T) and poly dAdT. 17 54

The sequences of two promoters recognized by the phage-specificied T7 RNA polymerase are presented. The two are identical in sequence but for one base pair from the initiation point (as determined by the 5' sequence of the transcripts), denoted +1, to position -15. The common : formula: (see text), sequence also includes a region of hyphenated twofold symmetry indicated by the boxes, with the twofold axis as the center of the six base-pair box. The heavy line indicates the extent of homology. The first promoter (A) is demonstrated to lie within gene 1, the gene for the polymerase itself, and 40 bases into the message transcribed from this promoter is found the R Nase III site separating genes 1 and 1.1. Binding of T7 RNA polymerase to these promoters is associated with a hyperchromic blue shift of the base chromophores consistent with partial melting of the base pairs at the promoter. Binding of T7 RNA polymerase to these promoters disappears at low pH and low temperature and is accompanied by a consequent loss of polymerase activity. The pH dependence of the binding step is adequately described by a single pK of 7.0. Polymerase catalytic activity, but not promoter binding, requires a single free sulfhydryl group of the enzyme with a pKa of approximately 7.8.
...
PMID:T7 RNA polymerase: promoter structure and polymerase binding. 36 3

Transcription by endogenous RNA polymerase B in lysates of Ehrlich ascites cells was investigated. The enzyme exhibits two salt optima at 0.025 M and at 0.3 M (NH4)2SO4 respectively. Preincubation of the cells with the nucleoside analogue 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole results in an inactivation of the polymerase molecules active under condition of low salt. This indicates two functional states of the enzyme in vivo. Initiations of RNA chains by polymerase B do not occur in vitro as judged by the incorporation of [beta-32P]GTP. Thus the two functional states seem to be both elongating polymerase molecules. Polymerase B does not occur in the lysates in a state ready to initiate on an exogenous template, in contrast to polymerase A and C which do occur in free form. Pretreatment with dichlororibofuranosylbenzimidazole in vivo does not result in an accumulation of free polymerase B.
...
PMID:On the activity of RNA polymerase B in lysates from Ehrlich ascites cells. 65 42

Avian erythroid cells were separated into five developmental stages by sedimentation on discontinuous isotonic albumin gradients. Solubilized enzyme activities from whole cells were partially purified and characterized by ion exchange and ion filtration chromatography and velocity sedimenttation analysis. Three nucleotide polymerase types were investigated: (a) DNA-dependent RNA polymerases; (b) RNA-dependent terminal ribonucleotidyltransferases, and (c) DNA-dependent DNA polymerases. The two characteristic forms of eucaryotic DNA-dependent RNA polymerases, polymerase I (nucleolar) and polymerase II (nucleoplasmic), were identified. Polymerase III was only marginally detectable even in the earliest developmental populations. At least two species of RNA-dependent terminal ribosyltransferases were present. One apparently was the poly(A) polymerase observed in other systems. The other terminal transferase was present in two chromatographic forms, required an RNA primer, and used UTP and/or CTP as particularly efficient substrates. Three DNA polymerase activities were resolved, two of which were characteristic of the alpha and beta DNA polymerases described in other eucaryotic systems. The third polymerase was not the gamma polymerase but a separate entity. Poly(dC)-dependent RNA polymerase activity, associated with the alpha polymerase, was relatively enriched in the third DNA polymerase species. The activity levels of the nucleotide polymerases were monitored as a function of red cell maturation. Characteristic declining patterns of activity were obtained for each enzyme which correlate well with the synthetic rates of their in vivo products where these are known. These results correlate well with the synthetic rates of their in vivo products where these are known. These results are consistent with the postulate that the general transcriptive and replicative control processes operating during development may involve changes in the level of the requisite polymerases.
...
PMID:Nucleotide polymerases in the developing avian erythrocyte. 83 21

Partially purified rat liver RNA polymerase I chromatographed on ribosomal RNA-Sepharose loses most (96%) of its activity assayed on native calf-thymus DNA templates, but loses little (8%) of its activity assayed on poly(deoxycytidylic acid) template. Polymerase I is not stimulated by polymerase II protein factor, or by bovine serum albumin. However, it is stimulated by histones, polylysine, and spermine. Addition of a protein fraction eluted by high ionic strength from the rRNA-Sepharose also restores activity on native calf-thymus DNA. Further purification yields a fraction containing two proteins of 11 000 and 12 000 molecular weight. Both proteins are distinct from histones by electrophoresis in sodium dodecyl sulfate and in acid urea. Both proteins are basic, insensitive to heat, bind to DNA, and stimulate polymerase I activity. The degree of stimulation of polymerase I is dependent upon both the enzyme/DNA and the factor/DNA ratio. The protein factors also stimulate polymerase II activity about half as effectively as polymerase I.
...
PMID:A protein cofactor that stimulates the activity of DNA-dependent RNA polymerase I on double-stranded DNA. 85 26

Three forms of RNA polymerase were assayed in nuclei and nucleoli isolated from rat liver and from Krebs II ascites cells. Assays of rat liver nuclei in the absence of exogenous DNA showed polymerase I accounted for 72% of the total activity, polymerase II for 17%, and polymerase III for 11%. The total activity in ascites nuclei was similar but the ratios of polymerase activities were different: polymerase I, 53%; polymerase II, 41%; and polymerase III, 6%. These values may reflect differences in the transcriptional activity of the nuclei. After isolation of nucleoli, both rat liver and ascites polymerase I accounted for 85% of enzyme activity. When exogenous calf-thymus DNA was added to nucleoli, there was a greater than 50% increase in activity suggesting that less than one-half of the polymerase I present was bound to endogenous template. Polymerase I was solubilized from either rat liver or ascites nucleoli by sonication at high ionic strength and subsequently purified by ion filtration, phosphocellulose, sucrose gradient centrifugation, and DNA-cellulose chromatography. The essentially homogenous ascites enzyme had a specific activity of 86 units/mg when assayed with native calf-thymus DNA and of 876 units/mg when assayed with poly(deoxycytidylic acid). Electrophoresis of the enzyme in sodium dodecyl sulfate indicated the presence of six subunits with molecular weights of 205 000, 125 000, 51 000, 44 000, 26 000 and 16 000. After the same purification procedure, the rat liver enzyme had a similar specific activity (98 units/mg) on native calf thymus and 362 units/mg on poly(deoxycytidylic acid).
...
PMID:Purification of rat liver and mouse ascites DNA-dependent RNA polymerase I. 85 54

After T4 bacteriophage infection of E. coli a complex series of events take place in the bacterium, including gross inhibition of host transcription and discrete changes in the classes of the genes of T4 that are transcribed. Accompanying these changes in the pattern of transcription one finds T4-induced changes in the RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase). The effects of modified polymerase on transcription can be advantageously analyzed in a DNA-directed cell-free system for protein synthesis. In this system gene activity is measured indirectly by the amounts and types of proteins sythesized. In the DNA-directed cell-free system this modified polymerase, like normal polymerase, transcribes T4 DNA with a high efficiency but transcribes bacteriophage lambda and host DNA very poorly. Polymerase reconstruction experiments show that modification of the alpha subunit of the RNA polymerase is sufficient for inhibition of host transcription. Host transcription is also inhibited in vitro by T4 DNA. This latter type of inhibition is presumed to involve competition between host DNA and T4 DNA for some factor essential for transcription. The T4-modified polymerase transcribes from T4 DNA many of the same genes as normal unmodified polymerase; it also shows a capability for transcribing certain "non-early" T4 genes which is enhanced in the presence of protein-containing extracts from T4-infected cells.
...
PMID:Effects of bacteriophage T4-induced modification of Escherichia coli RNA polymerase on gene expression in vitro. 110 8

Rats were fed for 6 days on a diet containing either 3 or 20% high-quality protein. Nuclei were isolated from liver and DNA-dependent RNA polymerases (EC 2.7.7.6) extracted with 1 M-(NH4)2SO4. The proteins were then precipitated with 3.5 M-(NH4)2SO4 and after dialysis applied to a DEAE-Sephadex column. The column was developed with a gradient of (NH4)2SO4. Polymerase I separated well from alpha-amanitin-sensitive polymerase II. The enzyme activities were compared between the two dietary groups. Rats that had received 3% protein showed a lower polymerase I activity per g wet wt. of liver, per mg of DNA and per mg of protein. Polymerase II was lower in activity per g wet wt. of liver and per mg of DNA, but was higher per mg of protein. Polyacrylamide-gel electrophoretograms showed a higher proportion of contaminating proteins in polymerase II fractions isolated from 20%-protein-fed rats. The data explain the lower activity obtained per mg of protein in these rats. It is concluded that a decrease in dietary protein content from 20 to 3% induces a fall in content and specific activity of RNA polymerase I and II in liver.
...
PMID:Deoxyribonucleic acid-dependent ribonucleic acid polymerase activity in rat liver after protein restriction. 115

The activation of the mouse embryo genome has been studied during early cleavage, in vivo. Individual embryos, prepared as whole mounts, were assayed for endogenous RNA polymerase activity. RNA synthesis was detected by autoradiography as the incorporation of [3H]UMP into an acid-insoluble product. No RNA polymerase activity could be detected in the pronuclei of one-cell embryos. Radioactive incorporation was first evident in the nuclei of two-cell embryos. This appeared to be confined to the nucleoplasm and could be abolished by alpha-amanitin but not by low concentrations of actinomycin D. Polymerase activity which was not affected by alpha-amanitin was first detected in the four-cell embryo, predominantly at the peripheries of the nucleoli. Nucleolar labelling increased markedly between subsequent cleavages, reaching a peak in early morulae. In one- and two-cell embryos, label incorporation could be found in the nucleus of the persisting polar body.
...
PMID:The RNA polymerase activity of the preimplantation mouse embryo. 119 32


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

---