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)

In vitro transcription was reconstituted with HeLa cell transcription factors and RNA polymerase II, which were essentially free from DNA topoisomerase activities. DNA templates with defined negative superhelical densities were tested for transcription activity. Transcription of the Bombyx mori fibroin gene increases and plateaus from templates of increasing superhelicity, and transcription from the adenovirus 2 major late promoter rises and then falls, while transcription of the Drosophila hsp70 gene remains unchanged. Dissection of transcription into pre and post-initiation steps by the use of Sarkosyl reveals that formation of a preinitiation complex on the fibroin gene or the adenovirus 2 major late promoter is slow on relaxed DNA and accelerated by DNA superhelicity. On the contrary, the preinitiation complex assembles rapidly on the hsp70 gene irrespective of DNA topology. As is the case with the fibroin gene promoter, DNA superhelicity appears to facilitate the interaction of transcription factor IID to the adenovirus 2 major late promoter.
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PMID:DNA superhelicity affects the formation of transcription preinitiation complex on eukaryotic genes differently. 164 22

Studies with yeast DNA topoisomerase mutants indicate that neither topoisomerase I nor II appears to be essential for transcription by RNA polymerase II. However, plasmids carrying transcriptionally active genes are found to be extremely negatively supercoiled when isolated from mutants lacking topoisomerase I. Supercoiling occurs during transcriptional elongation rather than during transcriptional activation. It takes place in the absence of topoisomerase I and does not seem to be dependent on topoisomerase II since it can occur at the nonpermissive temperature in a top1-top2 ts mutant. Whether this change in linking number is due to an unusual form of topoisomerase II or whether it is due to a new enzyme has yet to be determined. The results suggest that topoisomerase I is normally required to relax transcriptionally induced supercoils. A model is discussed which considers the role of topoisomerases in the movement of RNA polymerase along the DNA template.
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PMID:Transcription-dependent DNA supercoiling in yeast DNA topoisomerase mutants. 284 Feb 7

RNA polymerase I preparations purified from a rat hepatoma contained DNA topoisomerase activity. The DNA topoisomerase associated with the polymerase had an Mr of 110,000, required Mg2+ but not ATP, and was recognized by anti-topoisomerase I antibodies. When added to RNA polymerase I preparations containing topoisomerase activity, anti-topoisomerase I antibodies were able to inhibit the DNA relaxing activity of the preparation as well as RNA synthesis in vitro. RNA polymerase II prepared by analogous procedures did not contain topoisomerase activity and was not recognized by the antibodies. The topoisomerase I: polymerase I complex was reversibly dissociated by column chromatography on Sephacryl S200 in the presence of 0.25 M (NH4)2SO4. Topoisomerase I was immunolocalized in the transcriptionally active ribosomal gene complex containing RNA polymerase I in situ. These data indicate that topoisomerase I and RNA polymerase I are tightly complexed both in vivo and in vitro, and suggest a role for DNA topoisomerase I in the transcription of ribosomal genes.
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PMID:Association of DNA topoisomerase I and RNA polymerase I: a possible role for topoisomerase I in ribosomal gene transcription. 285 18

T4 DNA topoisomerase is a type II enzyme and is thought to be required for normal T4 DNA replication T4 gene 39 codes for the largest of the three subunits of T4 DNA topoisomerase. I have determined the nucleotide sequence of a region of 2568 nucleotides of T4 DNA which includes gene 39. The location of the gene was established by the identification of the first fifteen amino acids in the large open reading frame in the DNA sequence as those found at the amino-terminus of the purified 39-protein. The coding region of gene 39 has 1560 bases, and it is followed by two in-frame stop codons. The gene is preceded by a typical Shine-Dalgarno sequence as well as possible promoter sequences for E. coli RNA polymerase. T4 39-protein consists of 520 amino acids, and it has a calculated molecular weight of 58,478. By comparing the amino acid sequences, T4 39-protein is found to share homology with the gyrB subunit of DNA gyrase. This suggests that these topoisomerase subunits may be equivalent functionally. Some of the characteristics of the 39-protein and its structural features predicted from the DNA sequence data are discussed.
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PMID:Nucleotide sequence of a type II DNA topoisomerase gene. Bacteriophage T4 gene 39. 302 33

The RNA polymerase of HeLa cell mitochondria has been purified free of endonuclease and DNA topoisomerase activities, permitting evaluation of the effect of template topology on transcription in vitro. On single-stranded DNA templates, transcription is nonspecific and does not require mitochondrial DNA sequences. In contrast, duplex DNA templates are efficiently transcribed only when they (1) carry the mitochondrial D-loop region and (2) are negatively supercoiled. These findings suggest a role for template superhelicity in modulating mitochondrial transcription in vivo.
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PMID:Preference of human mitochondrial RNA polymerase for superhelical templates with mitochondrial promoters. 335 62

Several rifamycin derivatives inhibited the DNA-dependent RNA polymerase of African swine fever (ASF) virus particles. The inhibition was similar to that found with vaccinia virus RNA polymerase. Coumermycin A1, an inhibitor of type II DNA topoisomerases, inhibited strongly RNA synthesis in vitro by ASF virus particles. This suggests that transcription of ASF virus DNA requires a DNA topoisomerase.
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PMID:Effect of rifamycin derivatives and coumermycin A1 on in vitro RNA synthesis by African swine fever virus. Brief report. 662 87

A histone-like protein (H) from Escherichia coli has been purified to more than 98% homogeneity by using its capacity to inhibit DNA functions. H protein behaves as a dimer of 28,000-dalton subunits. The histone H2A-like properties of H protein are: (i) binding to DNA at a stoichiometry of 1 H protein dimer per 75 bases; (ii) abundance of about 30,000 molecules per cell, sufficient to bind about 20% of the chromosome; (iii) limiting digestion of double-stranded DNA by micrococcal nuclease; (iv) reannealing of complementary single-stranded DNA; (v) amino acid composition resembling that of eukaryotic histone H2A; (vi) neutralization of H protein by antibody specific for H2A; (vii) heat stability; and (viii) acid solubility. The capacity of H protein to bind DNA prevents its template or substrate functions n several reactions in vitro: DNA synthesis by several polymerases; transcription by RNA polymerase; DNA topoisomerase activity; and DNA-dependent ATP hydrolysis by rep protein, dnaB protein, or protein n'. Together with other histone-like proteins of E. coli, H protein may organize the E. coli chromosome into nucleosomes, such as in eukaryotic chromatin.
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PMID:Novel histone H2A-like protein of escherichia coli. 700 71

DNA supercoiling in eukaryotes is mediated by the process of chromatin assembly. This process couples the binding and wrapping of DNA around nucleosomal core particles and the enzymatic activity of DNA topoisomerase(s). Kmiec and Worcel (1985) reported that the binding of an RNA polymerase III transcription factor (TFIIIA) could accelerate DNA supercoiling catalysed by a Xenopus laevis cell-free extract. Although the reaction was repeatedly reproduced in the parent laboratory by numerous workers, another laboratory, interested in the molecular biology of TFIIIA, failed to reproduce TFIIIA-mediated supercoiling or gyration. In this review, an attempt is made to transcend personal beliefs and describe the experimental approaches used to clarify this issue. The original variability lay in the amount of endogenous RNA within the cell free extract and the concentrations of MgCl2 used to conduct the experiments.
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PMID:TFIIIA and DNA supercoiling: toward resolving a controversy. 750 21

The nucleotide sequence of a 55098 bp region from the right end of the genome of a virulent African swine fever virus (ASFV) isolate (Malawi LIL20/1) has been determined. Translation of the sequence identified 67 major open reading frames (ORFs) which are closely spaced and read from both DNA strands. At six positions intergenic tandem repeat arrays are found. Comparison of the predicted amino acid sequences of encoded proteins with protein sequence databases identified a number of homologies. These include three subunits of RNA polymerase, a protein with homology to transcription factor SII (TFSII), a DNA ligase, two subunits of mRNA capping enzyme, a DNA topoisomerase type II, a dUTPase, a protein kinase, three helicases, a ubiquitin-conjugating enzyme, a protein with homology to the nif S and nif S-like proteins identified in some bacteria and Saccharomyces cerevisiae, a protein with homology to both a myeloid differentiation primary response antigen (MyD116) and to a herpes simplex virus-encoded neurovirulence-associated protein (ICP34.5), a protein with homology to the ASFV-encoded structural protein p22, two proteins with homology to copies of the ASFV-encoded multigene family 360 and one protein with homology to the ASFV-encoded multigene family 110. Four genes encode proteins which have homology to each other and constitute a new multigene family (MGF100). Nine ORFs encode proteins which contain predicted transmembrane domains. The possible functions of these predicted ASFV-encoded proteins are discussed and the evolutionary relationship of ASFV to other viruses are considered. Despite the similarities in genome structure and replication strategy of ASFV with poxviruses, sequence similarity between them is low and the organization of ASFV-encoded genes is not colinear with that of the orthopoxviruses.
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PMID:Nucleotide sequence of a 55 kbp region from the right end of the genome of a pathogenic African swine fever virus isolate (Malawi LIL20/1). 802 96

Temperature-sensitive mutations (ts10, ts18, and ts39) of the vaccinia virus RNA helicase nucleoside triphosphate phosphohydrolase II (NPH-II) result in the production of noninfectious progeny virions at the restrictive temperature. The noninfectious mutant particles contain the wild-type complement of virion core and envelope polypeptides, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results of Western blot (immunoblot) analysis indicate that these particles lack NPH-II, whereas other enzymatic components of the virus core are present. These components include the following: DNA-dependent RNA polymerase subunits rpo147, rpo132, rpo94, rpo35, rpo30, rpo22, and rpo18; early transcription initiation factor subunits A8 and D6; mRNA capping enzyme subunits D1 and D12; RNA cap 2'-O-methyltransferase; A18 DNA helicase; DNA-dependent ATPase NPH-I; and DNA topoisomerase. Although RNA polymerase is encapsidated by the mutant viruses, mRNA synthesis in vitro by permeabilized mutant virions is only 5 to 20% that of the wild-type virus, as judged by nucleoside monophosphate incorporation into acid-insoluble material. Moreover, the transcripts synthesized by the mutant particles are longer than normal and remain virion associated. Transcription initiation by mutant virions occurs accurately at an endogenous genomic promoter, albeit at reduced levels (1 to 7%) compared with that of wild-type virions. In contrast, extracts of the mutant virions catalyze the wild-type level of transcription from an exogenous template containing an early promoter. We conclude that NPH-II is required for early mRNA synthesis uniquely in the context of the virus particle. Possible roles in transcription termination and RNA transport are discussed.
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PMID:Vaccinia virions lacking the RNA helicase nucleoside triphosphate phosphohydrolase II are defective in early transcription. 897 Sep 79


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