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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In search of an anti-transcriptase, antibody was raised in rabbits to partially purified, soluble NS protein present in cytoplasmic extracts of cells infected with the Indiana serotype of vesicular stomatitis (VSInd) virus. This antiserum gave specific reactions of identity by agar immunodiffusion with both cytoplasmic and virion NS protein. NS antiserum also preferentially precipitated NS 3-H-labeled protein from infected cytoplasmic extracts, whereas anti-whole VSInd virion serum also precipitated N 3-H-labeled protein from extracts both of infected cytoplasm and virion nucleocapsids. Transcriptase activity of VSInd cytoplasmic or virion-derived nucleocapsids was effectively inhibited by ribonuclease-free immunoglubulin prepared from homologous NSInd antiserum or from anti-whole vesicular stomatitis virus serum. Transcriptase activity of heterologous New Jersey serotype (VSNJ) nucleocapsids and virions was not appreciably affected by anti-NSInd or by anti-whole VSInd virion gamma globulin. Anti-NS gamma glubulin immediately switched off RNA synthesis by actively transcribing VSInd nucleocapsids, a finding which suggests that NS antibody inhibits RNA chain elongation.
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PMID:Inhibition of viral transcriptase by immunoglobulin directed against the nucleocapsid NS protein of vesicular stomatitis virus. 4 40

Recent findings have confirmed the role of form A DNA-dependent polymerase activity as that which is responsible for the transcription of the ribosomal RNA-coding genes. Unfortunately, the form A enzymes have proved to be very labile and difficult to work with, especially under high ionic strength conditions. We have, therefore, investigated a method for the purification of the form AI and AII enzymes from rat liver using mild low-ionic-strength conditions. Since preparations from whole nuclei were found to be grossly contaminated with protein having similar properties, the enzymes are extracted from nucleoli. Forms AI and AII are separated on a phosphocellulose column, purified by further ion-exchange chromatography, and by sedimentation through a glycerol gradient. The purified enzymes each migrate as a single band on native polyacrylamide gels and have the expected characteristics of form A RNA polymerase. Sedimentation rates through glycerol gradients indicate that they both have a similar size to that of Escherichia coli RNA polymerase (Mr about 500,000). The purified enzymes are free of DNase and RNase. A method is also described for the purification of form B from the nucleoplasm remaining after isolation of nucleoli. The presence of form C activity was not detected.
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PMID:Purification of form AI and AII DNA-dependent RNA polymerases from rat-liver nucleoli using low-ionic-strength extraction conditions. 5 56

Bleomycin (BLM) exclusively affects thymidine-containing compounds such as DNA and polydeoxyribonucleotides by releasing free thymine and leaving aldehyde functions. Molecular morphology and base sequence of the DNA strongly influence BLM activity. High BLM concentrations, besides modifying DNA into oligothyminic or athyminic nucleic acids, cause strand scissions. Enzymatic DNA and RNA synthesis is strongly influenced by BLM. The inhibition in DNA-dependent DNA polymerase and DNA-dependent RNA polymerase assays is of the non-competitive type. Protein biosynthesis in in vitro systems is not affected by BLM even at high concentrations. BLM turns out to be a strong inhibitor of DNase I and of DNase II; the inhibition is of the competitive type. The enzymatic activities of nucleases using RNA as substrate (RNase A, RNase B, Rnase T1, venom phosphodiesterase I and spleen phosphodiesterase II) are not influenced by this antibiotic. The antibiotic reduces cell proliferation (L5178y mouse lymphoma cells) in vitro in low concentrations by cytostasis and at higher concentrations by cytotoxicity. In BLM-treated L5178y cells, DNA synthesis is strongly reduced, while RNA and protein synthesis are not affected. In vivo, using growing quail oviducts, cell proliferation and cytodifferentiation are markedly inhibited after BLM treatment. This is attributed to the observed inhibition of DNA synthesis. RNA and protein synthesis as well as gene expression are not influenced by BLM under the conditions used. The selective inhibition of DNA synthesis in vivo may be caused by the following mechanisms: (1) competition of BLM with RNA; (2) blocking of the accessibility of DNA in chromatin to BLM, and (3) dependence from the repair processes. BLM inhibits growth of sarcomas, induced by oncogenic RNA viruses in vivo; well-developed tumours show regression after BLM treatment. Transformation of chick embryo fibroblasts by oncogenic RNA viruses in vitro and growth of these viruses is blocked by BLM; the most sensitive period for BLM inhibition is the time during the first period (integration of viral genome into cellular genome?) after infection.
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PMID:Effect of bleomycin on DNA, RNA, protein, chromatin and on cell transformation by oncogenic RNA viruses. 6 69

Rabbit globin complementary DNA made with RNA-dependent DNA polymerase (reverse transcriptase) was used as a template for in vitro synthesis of 32P-labeled RNA and deoxysubstituted RNA. The sequences of the nucleotides in most of the fragments resulting from combined ribonuclease T1 and alkaline phosphatase digestion have been determined. In addition, the 3' nearest neighbor was determined for several fragments resulting from digestion with T1 ribonuclease. The utility of the deoxysubstitution technique was demonstrated by the ease with which the sequences of pyrimidine-rich fragments could be determined. Many sequences thus determined were long enough to fit uniquely with the alpha- or beta-globin amino acid sequences. The positions of these fits were found to be clustered, leading us to believe that only certain regions of the complementary DNA are transcribed by Escherichia coli RNA polymerase. Other unique characteristics of RNA synthesis from a complementary DNA template include a high yield of free poly(A) and the fact that one must use low rather than high salt buffers to obtain transcripts of high molecular weight.
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PMID:Rabbit globin mRNA: analysis of T1 RNAse digestion fragments. 6 35

The sequence of 129 nucleotides next to the poly(A) tail of encephalomyocarditis virus RNA has been determined by rapid gel sequencing of cDNA synthesized with DNA polymerase I or reverse transcriptase and a phasing primer, [5'-32P]p(dT)8dC. The sequence is in accord with (a) the pyrimidine tracts which were mapped in blocks along the cDNA, (B) the sequences of seven characteristic T1 RNase oligonucleotides in the RNA transcribed from the cDNA with RNA polymerase, and (c) a limited amount of sequence deduced by partial spleen phosphodiesterase digestion and depurination of endonuclease IV oligonucleotides. The 3' end shows little secondary structure on its own. Ten nonsense codons block all three reading frames such that at least 26 nucleotides do not code for protein. The possible function of a homology A-A-U-A-A-A with other polyadenylated RNAs is discussed.
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PMID:Sequence of 129 nucleotides at the 3'-terminus of encephalomyocarditis virus RNA. 7 85

Hormones play a role in the regulation of gene expression by inducing changes in enzyme patterns in target cells mediated by the synthesis of specific RNA molecules. Erythropoiesis has been used as a system for studying the molecular mechanism of regulation of gene action by means of two hormones: erythropoietin and testosterone. Experiments designed to correlate the biochemical action of both hormones on rat marrow cells are herein reported. Both factors seems to act at different biochemical and citological levels. Erythropoietin triggers the erythropoietic process acting on the erythropoietin sensitive cells (ESC), in which the hormone induces the synthesis of a high molecular weight RNA, which is the precursor of a functional 9 S messenger RNA. Testosterone seems to act on polychromatophilic erythroblasts, in which the synthesis of ribosomal RNA or its precursor is stimulated. The steroid enhances the nuclear ribonuclease activity, which could represent a control mechanism for the processing (maturation) of high molecular weight RNAs. The incorporation of 3H-GTP and 3H-UTP into RNA by isolated rat bone marrow nuclei is stimulated by erythropoietin and testosterone. Using alpha-amanitine and different ionic strength conditions it was found that erythropoietin enhances preferentially RNA polymerase II activity while testosterone increases RNA polymerase I activity. It is postulated that erythropoietin and testosterone act synergically to create the biochemical machinery for hemoglobin synthesis, the macromolecule that characterizes the erythropoietic process.
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PMID:Hormonal control of gene expression: differential activation of rat bone marrow RNA polymerases by erythropoietin and testosterone. 9 87

Several in vitro properties of partially purified form II RNA polymerase from Drosophila melanogaster embryo nuclei are described. The enzyme preparation is free from contaminating RNase, protein kinase, and polyphosphate kinase activities and can be used to study the incorporation of gamma-32P-labeled nucleoside triphosphates. The enzyme exhibits a biphasic heat inactivation pattern which is probably related to differential lability of its two subforms. However, a considerable protection against heat inactivation is provided by the nucleoside triphosphates present in the in vitro reaction system such that the enzyme catalyzes RNA synthesis in a nearly linear mode for over 2 hr at 30 C. Two initiation inhibitors, rifamycin AF/013 was found unsuitable for critical studies because of the high concentrations necessary for total inhibition (200 micrograms/ml) and particularly because of the obligate use of solvents which secondarily have a destabilizing effect on native DNA. Poly[I] was found to effectively block initiation at very low concentrations (1 microgram/ml). The enzyme rapidly forms poly[I]-resistant preinitiation complexes on both double- and single-stranded DNA. These complexes decay with a half-life of 2.5--3 min. RNA synthesis from poly[I]-resistant complexes amounts to 10% of the total potential synthesis on both double- and single-stranded DNA. Enzyme-DNA saturation experiments indicate that the form II enzyme discriminates two types of sites on Drosophila DNA, tight binding and weak binding, from which RNA synthesis proceeds slowly and rapidly, respectively. The tight-binding sites appear to be analogous to those sites with which the enzyme is able to form poly[I]-resistant complexes.
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PMID:Form II DNA-dependent RNA polymerase from Drosophila melanogaster: general in vitro catalytic properties and template interactions. 11 Mar 17

Fidelity of preribosomal RNA transcription in vitro was studied after selective deproteinization of nucleoli using either sequential salt extraction or sodium deoxycholate treatment. Homochromatography fingerprinting and identification of marker oligonucleotides from a T1 ribonuclease digest of the transcripts were used to evaluate the RNA products. These studies indicated that: (1) nucleoli retained their endogenous RNA polymerase I activity and the specificity of transcription up to 0.6 M NaCl extraction; (2) exogenous RNA polymerase I transcribed nucleolar chromatin only after 1.0 M NaCl extraction and the transcription pattern, like that of totally deproteinized DNA, was completely random; (3) extraction of nucleoli with deoxycholate resulted in a DNP complex in which the endogenous RNA polymerase I transcribed pre-rRNA specifically; however, it also initiated random transcription, producing a "mixed" fingerprint pattern on the homochromatogram. The random transcription was selectively inhibited either by deoxycholate or rifampicin AF/013. These studies indicate that the selectivity of pre-rRNA transcription is due both to the endogenous RNA polymerase I molecules that were involved in transcription in vivo and are tightly bound to the template and to factors in intact nucleoli which prevent random transcription by the released RNA polymerase I molecules.
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PMID:Studies on the specificity of preribosomal RNA transcription in nucleoli after selective deproteinization. 11 95

Nucleoli isolated from Novikoff hepatoma cells of the rat were previously shown to carry out synthesis of predominantly ribosomal precursor RNA and methylation of this RNA in vitro. In order to develop in vitro systems for further detailed study of these processes and their interrelationships, isolated nucleoli were incubated in a complete RNA-synthesizing medium using (5-3H)cytidine 5'-triphosphate or S-adenoxyl(methyl-3H)methionine to measure the activities of RNA synthesis and methylation, respectively, under the same reaction conditions. Methylation of the ribose of the nascent ribosomal precursor RNA predominated. It occurred in close coordination with the transcriptional step by RNA polymerase as shown by the kinetic data, the analysis of labeled RNA in sucrose gradients, the inhibition by increased ionic strength or actinomycin D, and the release of labeled nucleotides by a 3'-exonuclease, venom phosphodiesterase. Methylation of the RNA bases occurred more slowly, continued longer after transcription ceased, and appeared to follow later in the processing of the RNA. Certain divalent cations (Mg2+, Mn2+, and Ca2+ at higher concentrations, and Zn2+ and Cu2+) inhibited both RNA synthesis and methylation to similar extents. RNase inhibitors (bentonite and dextran sulfate) at low concentration inhibited methylation while stimulating RNA synthesis, and pyrophosphate greatly decreased RNA synthesis with relatively little effect on methylation. These results indicated that RNA polymerase and ribosomal RNA methylases can function independently despite their close relationship. An exogenous substrate for the nucleolar rRNA methylases was found: nuclear RNA prepared from Novikoff hepatoma cells, cultured in the absence of methionine, served as a good substrate for methylation of both ribose and bases. Other exogenous RNAs, including cytoplasmic ribosomal RNA from these methionine-starved cells, nucleolar RNA from normal cells, and wheat germ ribosomal RNA were almost devoid of methyl-acceptor activity. A description of these parameters helps establish isolated nucleoli as a suitable system for further study of interaction of RNA polymerase, methylases, and nucleases in control of synthesis of ribosomal RNA.
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PMID:Interrelationships between synthesis and methylation of ribosomal RNA in isolated Novikoff Tumor nucleoli. 16 25

When closed circular SV40 DNA containing 58 negative superhelical turns is used as a template for RNA synthesis with Escherichia coli RNA polymerase, a fraction of the RNA product remains complexed with the DNA. The RNA in the complex is resistant to ribonuclease in high salt, and the Tm indicates that it is hydrogen bonded to the DNA. The mole ratio of RNA to DNA nucleotides in the complex ranges from 0.01 to 0.08; the RNA ranges in length from 80 to 600 nucleotides. The formation of the complex is dependent on the circular DNA being topologically underwound since no complex is formed when closed circular DNA containing zero superhelical turns is used as the template. The DNA-RNA complex can serve as a primer-template combination for in vitro DNA synthesis by E. coli DNA polymerase I. After synthesis with (alpha-32P)-labeled deoxyribonucleoside triphosphates followed by alkaline hydrolysis, the isolation of 32P-labeled ribonucleotides is evidence for a covalent linkage between the RNA and the DNA synthesized. During the in vitro DNA synthesis, the template is nicked at a low rate, and the nicked molecules support extensive DNA synthesis. This observation indicates that only limited synthesis can occur on unnicked molecules possibly owing to the topological constraints against unwinding of the helix. Possible models for in vivo priming of double-stranded DNA by E. coli RNA polymerase are discussed.
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PMID:Priming of superhelical SV40 DNA by Escherichia coli RNA polymerase for in vitro DNA synthesis. 16 2


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