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)

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

The activities of streptovaricin complexes, streptovaricins, streptovals, and streptovarinic degradation products were elevated against RNA-directed DNA polymerases of Rauscher leukemia virus, DNA-dependent DNA polymerase of bacterial and mammalian cells, and DNA-dependent RNA polymerases of mammalian origin. The activities of streptovaricins were also listed for comparison purposes. The effects of streptovaricin complexes on viral DNA polymerases varied significantly from lot to lot, and streptovaricin complex lot 7 was the most active. All the streptovals and streptovaricin degradation products except varicinal A showed a marked improvement (twofold to tenfold) in activity against the viral enzyme over the parent streptovaricins. None of these compounds, however, displayed any significant effect on either the DNA polymerase of L1210 leukemia cells and Escherichia coli or the RNA polymerase of isolated nuclei of mouse liver. As a result of tests in these systems, some specific inhibitors of RNA-directed DNA polymerases of Rauscher leukemia virus were selected.
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PMID:Effects of streptovaricins and their degradation products on RNA-directed DNA polymerase of Rauscher leukemia virus. 6 15

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.
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PMID:Gene specific priming of complementary DNA synthesis. 6 22

The alpha, beta2, and alphabeta forms of the RNA-dependent DNA polymerase of avian sarcoma virus B77 grown in duck embryo fibroblasts have been compared with respect to several kinetic properties. The following results were obtained. 1. The Km values for dTTP and dGTP for enzyme forms alpha, beta2, and alphabeta were 77, 39, and 74, and 6.8, 3.1, and 6.1 micronM, respectively. 2. The affinity of 70 S Rous sarcoma virus RNA for enzyme form alphabeta was about twice that for the other two forms. 3. The relative specific activities of the three enzyme forms on synthetic primer-templates such as poly(rA)-poly(dT) were almost the same. The viral 70 S RNA-dependent specific activities were 2 to 3 orders of magnitude lower and in the ratio of 1:3:5 for enzyme forms alpha:beta2:alphabeta. Addition of exogenous oligo(dT) stimulated the 70 S viral RNA-dependent activity of enzyme forms alphabeta and beta2 by a factor of 3, and that of enzyme form alpha by a factor of 30, so that it then became the most active transcriptase of viral 70 S RNA. 4. The largest transcripts formed by the three enzyme forms with 70 S viral RNA as primer-template were about 4,500 nucleotides long. About one-third of the total amount of polynucleotides polymerized by the alphabeta enzyme was in the form of such transcripts. This proportion was far higher than for the other two enzyme forms. 5. All three enzyme forms were capable of transcribing single-stranded into double-stranded DNA. 6. The 3-propylcyclohexyl piperidyl derivative of rifamycin SV, at a concentration of 100 microng/ml, inhibited enzyme forms beta2 and alphabeta by over 99.5 and 96%, respectively, but enzyme form alpha by only about 60%. 7. The beta2 and alphabeta forms of the enzyme were processive DNA polymerases, the alpha form a nonprocessive polymerase. 8. In general, these results indicate that in most respects the properties of the dimeric enzyme forms resemble each other much more closely than those of the alpha form. In some very important respects, such as affinity for viral RNA and the size of transcripts formed from it, the alphabeta enzyme form performs significantly better than either of the other two enzyme forms.
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PMID:RNA-dependent DNA polymerase of avian sarcoma virus B77. II. Comparison of the catalytic properties of the alpha, beta2, and alphabeta enzyme forms. 6 35

This paper describes a novel biochemical effect of gramicidin, a class of peptide antibiotics produced by Bacillus brevis during the transition from vegetative growth to sporulation. Gramicidin inhibits RNA synthesis by purified RNA polymerase (nucleosidetriphosphate:RNA nucleotidyl-transferase, EC 2.7.7.6) by interfering with the binding of RNA polymerase to DNA. This effect seems to involve the destabilization of the "open" RNA polymerase-DNA complex, a mode of action consistent with the control of promoter selection. Selectivity in the inhibition of RNA synthesis by gramicidin is observed when transcription is partially blocked by low levels of actinomycin D. Since the inhibition of RNA synthesis by gramicidin is obtained in a highly purified system devoid of membranes, it must be distinct from the ionophoretic activity of the antibiotic. It is possible that this new mode of action reflects the function of gramicidin during bacterial sporulation.
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PMID:Biological function of gramicidin: selective inhibition of RNA polymerase. 6 2

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 sporulating bacterial strain Bacillus brevis (ATCC 8185) produces two types of peptide antibiotics, the linear gramicidins and the cyclic tyrocidines. Their effects on transcription in vitro were studied: 1. RNA synthesis catalized by RNA polymerase and DNA as template, both from B. brevis cells, is inhibited by the addition of gramicidin maximally to 50% as compared to controls without gramicidin. This inhibition is dependent on the concentration of gramicidin as well as on that of RNA polymerase. 2. Transcription of DNA is also inhibited by tyrocidine. This inhibition is partially compensated by the addition of gramicidin. Here, the action of gramicidin is again dependent on its concentration and on that of RNA polymerase. 3. This counteraction of gramicidin occurs only with RNA polymerase from B. brevis. Enzyme preparations of other origin are additively inhibited by gramicidin when previously inhibited by tyrocidine. The specific action pattern of gramicidin and tyrocidine in connection with the B. brevis RNA polymerase supports the notion that the two peptide antibiotics may be involved in a gene regulatory mechanism during sporogenesis.
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PMID:The peptide antibiotic gramicidin D. A specific reactivator of tyrocidine-inhibited transcription. 6 43

DNA complementary in sequence to the messenger RNA for pre-proparathyroid hormone was synthesised using reverse transcriptase. In a linked transcription-translation system using RNA polymerase and cell-free extract from wheat germ, the DNA directed the synthesis of a protein identified as pre-proparathyroid hormone by N-terminal sequencing and by electrophoretic and immunologic criteria.
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PMID:DNA complementary to parathyroid mRNA directs synthesis of pre-proparathyroid hormone in a linked transcription-translation system. 7 Jul 56

Continuous monitoring of enzymes, particularly those involved in nucleic acid synthesis could be a useful means of detecting infections and abnormalities in cells in culture. Model systems using mouse (3T3), human (MRC-5) and chick embryo cells infected with RNA tumour viruses were studied. Reverse transcriptase activities were determined by the incorporation of (3H) nucleotides into synthetic primer-templates or into complementary DNA of endogenous RNA and characterised by their specificity for primer-templates dT12-18.rAn, dG12-18.rCn, dT12-18.DAn and dG10.rCmn, their requirements for metal ions and inhibition by antisera. Measurement of reverse transcriptase is a more sensitive method than the COFAL test for the detection of RAV infection of chick cells. Iododeoxyuridine, bromodeoxyuridine and dexamethasone, which can induce latent C viruses, have no effect on MRC-5 cells; no increases in reverse transcriptase were detected and no C particles were seen by electron microscopy. Solid tumours developed in immunosuppressed mice injected s/c with 3T3 and MRC-5 cells chronically infected with MLV but none formed after injection of cells or virus suspension alone. Thymidine kinase activities of WI-38 and MRC-5 cells are greatly increased by infection with CMV or transformation with SV40. Mammalian tumours and tumour cell lines also show a high specific activity of cytoplasmic thymidine kinase.
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PMID:Reverse transcriptase and thymidine kinase as markers for tumorigenicity and viral contamination of cells. 7 84

Two maxima of optic density were observed at zones of gravity 1.27 g/ml and 1.15-1.16 g/ml by sedimentation equilibrium in sucrose gradient of cultural fluid, obtained from the transplantable cells of the HEP-2 strain and concentrated by ultracentrifugation. These fractions thus isolated were tested for presence of RNA- and DNA-dependent DNA-polymerase. The structures with the density of 1.15-1.16 g/ml were identified with the oncornaviruses on the basis of characteristics flotating density, presence of RNA-dependent DNA-polymerase. Analyses of products of RNA- and DNA-dependent polymerases reaction, flotating density of oncornaviral nucleotides in sucrose and CsCl gradients are presented. The optimal conditions for reverse-transcriptase reaction of virions of D type viruses are characterized.
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PMID:[Further study of spontaneous virus production using transplantable HEp-2 cells as a model]. 7 26


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