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)

1. In order to demonstrate that triiodothyronine affects mitochondrial RNA synthesis by acting on the enzyme component of the DNA. RNA polymerase complex, mitochondrial RNA polymerase from thyroidectomized and hormone-treated rats was purified up to a stage in which activity was dependent on the addition of exogenous template. In these conditions and using different DNAs as templates, the enzyme from hormone-treated animals displayed an activity about double that of the activity of thyroidectomized animals. 2. Measurements of stability of mitochondrial RNA synthesized in vitro suggest, however, that the hormone can act also at the template level in mitochondrial transcription: the RNA population synthesized in vitro from hormone-treated rats is indeed much more enriched in unstable, probably messenger, RNA species. 3. The turnover of mitochondrial messenger RNA is higher after hormone treatment. 4. Adenosine cyclic 3':5'-monophosphate (cAMP) and its dibutyryl derivative added in vitro to mitochondria from thyroidectomized animals do not affect the incorporation of labeled precursor into mitochondrial RNA, suggesting that the level of the cyclic nucleotide in mitochondria is probably not involved in the hormone action. 5. It is concluded from these and previous studies that the thyroid hormone affects more than one parameter in the mitochondrial transcription process. The interrelationship between these events at molecular level remains, however, to be clarified.
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PMID:Effects of triiodothyronine on rat-liver mitochondrial transcription process. 16 68

The mechanism of the priming effect of luteinizing hormone releasing factor (LH-RF) upon gonadotrophin secretion was studied using short-term incubation of hemipituitary glands from pro-oestrous rats. The dependence of the priming, but not the LH releasing action of LH-RF on protein synthesis in pituitary tissue was confirmed. Cytochalasin B failed to affect the first response to LH-RF, but abolished the priming effect, suggesting that the integrity of cellular microfilaments was essential. Colchicine and vinblastine did not modify the response to LH-RF. Neither inhibitors of DNA nor the inhibitor of RNA polymerase II, alpha-amanitin, significantly affected the priming action of LH-RF. Normal extracellular concentrations of Ca2+ were necessary for gonadotrophin release, but the priming effect was not significantly affected by low extracellular Ca2+ and could not be elicited by raising intracellular Ca2+ concentrations. Adenosine 3':5'-cyclic phosphate did not appear to act as a second messenger for either the gonadotrophin releasing or the priming action of LH-RF.
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PMID:Priming effect of luteinizing hormone releasing factor in vitro: role of protein synthesis, contractile elements, Ca2+ and cyclic AMP. 22 30

Adenosine 2',3'-riboepoxide 5'-triphosphate (epoxyATP) has been found to be a suicidal inactivator of DNA polymerase I from Escherichia coli by the following criteria. Inactivation is complete, is first order in enzyme activity, and shows saturation kinetics with an apparent KD of 30 +/- 10 micron for epoxy ATP. This KD is comparable to the KM of the substrate dATP. The t1/2 for inactivation is 1.3 min. Inactivation requires Mg2+ and the complementary template. The enzyme is protected by dATP but not by an excess of template. Gel filtration of the reaction mixture after inactivation with [3H]epoxy ATP results in the comigration of E. coli DNA polymerase I, the tritium-labeled inactivator, and the DNA template. The stoichiometry of binding approaches 1 mol of [3H]epoxy nucleotide per mol of inactivated enzyme. These results are consistent with the hypothesis that epoxy ATP initially serves as a substrate for the polymerase reaction, elongating the DNA chain by a nucleotidyl unit, and subsequently alkylates an essential base at the primer terminus binding site of the enzyme. Epoxy ATP also inactivates human and viral DNA polymerases but not E. coli RNA polymerase or rabbit muscle pyruvate kinase. Hence epoxy ATP may be a specific suicide reagent for DNA polymerases.
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PMID:Apparent suicidal inactivation of DNA polymerase by adenosine 2',3'-riboepoxide 5'-triphosphate. 34 91

The rational design of antitumor and antiviral agents must ultimately take advantage of biochemical differences between normal host cells and transformed cells. The initial experiments must be performed with subcellular or cellular model systems. For the studies with arabinosyl nucleosides we have chosen those enzyme systems, synthesizing DNA and RNA; being precursor analogues, the different arabinosyl nucleosides have been added in the triphosphate state to the different DNA- and RNA polymerase assays. 1-beta-D-Arabinofuranosylcytosine-5'-triphosphate has been found to inhibit the RNA-dependent DNA polymerases (isolated from oncogenic RNA viruses) 200-fold more sensitively than viral and cellular DNA-dependent DNA polymerases. Recent results, showing that RNA-leukemia-virus-related sequences are present in DNA of some human leukemia patients might support the assumption that the efficacy of this antimetabolite in the treatment of acute leukemia is due to its, at least relative selective inhibitory activity on reverse transcriptase. 9-beta-D-Arabinofuranosyladenine-5'-triphosphate is a strong inhibitor of cellular DNA polymerases with the cytological consequence of an inhibition of cell proliferation. The clinical benefit of the compound in treatment of tumors is dependent on their levels of adenosine deaminase. The triphosphate of this compound is a 100-fold more sensitive inhibitor of the herpesvirus DNA polymerase compared to the cellular replicative DNA polymerase. In addition the analogue, incorporated into herpesvirus DNA, acts as chain terminator. These effects are the biochemical basis for the highly selective antiherpesvirus activity of this antimetabolite. The anomer 9-alpha-D-arabinofuranosyladenine-5'-triphosphate only inhibits cellular replicative DNA polymerase and has no effect on herpesvirus DNA polymerase. Consequently this agent acts only cytostatically and not antivirally. Concerning 1-beta-D-arabinofuranosyluracil and 1-beta-D-arabinofuranosylthymine no pronounced antitumor or antiviral effect is known.
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PMID:Rational design of arabinosyl nucleosides as antitumor and antiviral agents. 61 2

Adenosine (beta,gamma-imido)triphosphate (AMP-PNP) and guanosine (beta,gamma-imido)triphosphate (GMP-PNP) are analogs of ATP and GTP with non-hydrolyzable gamma-phosphates. Although both AMP-PNP and GMP-PNP were used in place of ATP and GTP by Escherichia coli RNA polymerase to transcribe vaccinia virus DNA, only GMP-PNP was used by the transcriptase present within vaccinia virus cores. AMP-PNP specifically prevented initiation of transcription, since RNA initiated in the presence of ATP, GTP, and CTP was subsequently elongated by incubating the washed cores in the presence of AMP-PNP, GTP, CTP, and UTP. The RNA formed in this manner, however, was (i) several times longer than normal transcripts, indicating a defect in chain termination and/or cleavage of nascent RNA, (ii) was not polyadenylylated (although free polyadenylic acid formed), and (iii) was not extruded from the virus cores. Nearest neighbor analysis demonstrated that AMP-PNP was incorporated adjacent to all four nucleotides, and hybridization to restriction endonuclease fragments of vaccinia virus DNA indicated that the high-molecular-weight RNA was transcribed from representative fractions of the entire genome. The possibility of a block in processing rather than or in addition to a block in chain termination was suggested by the cleavage of the high-molecular-weight RNA within the core after replacement of AMP-PNP with ATP. Cleavage of purified high-molecular-weight RNA by a soluble endoribonuclease extracted from vaccinia virus cores, however, was not dependent upon ATP, nor was it inhibited by AMP-PNP. The latter results suggest that AMP-PNP blocks a step preceding cleavage.
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PMID:Multiple roles for ATP in the synthesis and processing of mRNA by vaccinia virus: specific inhibitory effects of adenosine (beta,gamma-imido) triphosphate. 69 Nov 15

The 3'-terminal colicin fragments of 16S ribosomal RNA were isolated from Bacillus stearothermophilus and from its kasugamycin-resistant (ksgA) derivative lacking N6-dimethylation of the two adjacent adenosines in a hairpin loop. The fragment from the ksgA strain still contains a naturally occurring N2-methylguanosine in the loop. An RNA molecule resembling the B. stearothermophilus colicin fragment but without modified nucleosides was synthesized in vitro using a DNA template and bacteriophage T7 RNA polymerase. Proton-NMR spectra of the RNAs were recorded at 500 MHz. The imino-proton resonances of base-paired G and U residues could be assigned on the basis of previous NMR studies of the colicin fragment of Escherichia coli and by a combination of methylation-induced shifts and thermal melting of base pairs. The assignments were partly confirmed by NOE measurements. Adenosine dimethylation in the loop has a distinct conformational effect on the base pairs adjoining the loop. The thermal denaturation melting curve of the enzymatically synthesized RNA fragment was also determined and the transition midpoint (tm) was found to be 73 degrees C at 15 mM Na+. A comparison with previously determined thermodynamic parameters for various colicin fragments demonstrates that base methylations in the loop lead to a relatively strong destabilization of the hairpin helix. In terms of free energy the positive contribution of the methylations are in the order of the deletion of one base pair from the stem. Other data show that recently published free-energy parameters do not apply for certain RNA hairpins.
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PMID:Conformational and thermodynamic effects of naturally occurring base methylations in a ribosomal RNA hairpin of Bacillus stearothermophilus. 169 Jun 48

Antibodies against adenosine markedly inhibited in vitro transcription in isolated BHK 21 nuclei in a dose-dependent manner. The inhibition was specific as it could be completely reversed by the addition of homologous hapten. Addition of RNA at low concentration reversed the inhibition, whereas excess DNA did not have any effect. Adenosine antibodies also inhibited in vitro transcription with calf thymus DNA and E. coli RNA polymerase. Antibodies that react with DNA but not with RNA such as anti-dpA, anti-dpC and anti-DNA failed to inhibit in vitro transcription in isolated nuclei as well as with calf thymus DNA and E. coli RNA polymerase. The results strongly indicate that the binding of adenosine antibodies to RNA is responsible for the inhibition of transcription.
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PMID:Inhibition of in vitro transcription by adenosine antibodies. 224 89

Adenosine, TMP, ADP, ATP and UpA along with guanosine and tis analogous derivatives have different reactivity towards [alpha-32P]UTP in abortive initiation reactions catalyzed by E. coli RNA polymerase on T2 DNA in the presence of Mg2+ or Mn2+. Rifampicin moderately inhibited almost all of the above mentioned reactions, except the ATP and the GTP which were even 2.5 times more reactive in the presence of this antibiotic.
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PMID:[Participation of various adenosine and guanosine derivatives in the abortive RNA synthesis initiation reaction: effect of Mg2+, Mn2+, and rifampicin]. 616 Mar 85

Adenosine 5'-O-(2-thiotriphosphate) (ATP beta S) and guanosine 5'-O-(2-thiotriphosphate) (GTP beta S) were used to demonstrate initiation of mouse mammary tumor virus (MMTV) RNA in preparations of whole nuclei from control and glucocorticoid-treated MMTV-infected rat hepatoma tissue culture cells. RNA chains initiated in the cell-free reaction retain a thiol group at the 5' end and can be separated from thiol-free RNA chains by chromatography on mercury-Sepharose. The abundance of MMTV sequences was determined by nucleic acid hybridization with filter-bound DNA representing four different regions of the MMTV genome. About six times more MMTV RNA is initiated with GTP beta S than with ATP beta S. Most of the cell-free initiation of MMTV RNA occurs within or very near a 380-nucleotide section of the proviral long terminal repeat that is the presumptive site of transcription initiation in vivo. The sensitivity of MMTV RNA initiation and synthesis to alpha-amanitin and actinomycin D are characteristic of DNA-directed transcription by RNA polymerase II. Nuclei from glucocorticoid-treated cells initiate approximately 10 times more MMTV RNA than nuclei from control cells.
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PMID:Region-specific initiation of mouse mammary tumor virus RNA synthesis by endogenous RNA polymerase II in preparations of cell nuclei. 629 6

Adenosine N1-oxide (ANO) is a potent and highly selective inhibitor of vaccinia virus replication. We examined the impact of ANO on vaccinia virus macromolecular synthesis during synchronous infection of BSC40 cells. Viral DNA replication and viral late protein synthesis were blocked completely by ANO, effects that were attributable to a defect in the expression of viral early genes. Vaccinia virus early proteins were not synthesized in the presence of ANO, even though vaccinia virus early mRNAs were produced. Cellular protein synthesis was unaffected by ANO, and virus infection in the presence of the drug did not elicit the normal shutoff of host protein synthesis. Adenosine N1-oxide triphosphate (ANO-TP), the predominant metabolite of the drug in vivo, could substitute for ATP in RNA synthesis by purified vaccinia virus RNA polymerase. ANO-TP could support early transcription by purified virions if dATP was provided as an energy source. ANO-TP did not inhibit early transcription in the presence of ATP. These findings suggest a novel antiviral mechanism whereby incorporation of a modified nucleotide into viral mRNAs might selectively block viral gene expression at the level of translation. We believe that ANO merits consideration as an antipoxvirus drug for topical treatment of molluscum contagiosum in humans.
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PMID:Adenosine N1-oxide inhibits vaccinia virus replication by blocking translation of viral early mRNAs. 766 36


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