Showing papers on "RNA published in 1970"
TL;DR: Two independent groups of investigators have found evidence of an enzyme in virions of RNA tumour viruses which synthesizes DNA from an RNA template, apparently the classical process of information transfer from DNA to RNA can be inverted.
Abstract: Two independent groups of investigators have found evidence of an enzyme in virions of RNA tumour viruses which synthesizes DNA from an RNA template. This discovery, if upheld, will have important implications not only for carcinogenesis by RNA viruses but also for the general understanding of genetic transcription: apparently the classical process of information transfer from DNA to RNA can be inverted.
1,872 citations
TL;DR: Over the range of actinomycin concentrations employed cellular uptake of the drug is proportional to external concentration, and maximal inhibition of RNA synthesis is generally achieved within one hour after exposure.
Abstract: A quantitative dose-response study was made of the inhibition by actinomycin D of the synthesis of various RNA species in cultured L cells. After a suitable preincubation with various concentrations of actinomycin, synthesis was measured by a brief incorporation of radioactive uridine. The 45S precursor of ribosomal RNA, 5S ribosomal RNA, transfer RNA and various sized fractions of heterogeneous nuclear RNA were extracted from the appropriate subcellular fractions and resolved by acrylamide gel electrophoresis. Polyribosomal messenger RNA was also studied. Over the range of actinomycin concentrations employed cellular uptake of the drug is proportional to external concentration, and maximal inhibition of RNA synthesis is generally achieved within one hour after exposure.
For most of the RNA species studied the dose-response data appear to follow an exponential inactivation function with some “tailing” evident at the higher doses. Sensitivities, defined as the reciprocal of the dose necessary to reduce synthesis to 1/e of the control level, were compared and examined with respect to the molecular weight of the RNA species under consideration. Among the heterogeneous nuclear RNA's there is a good correlation between RNA size and sensitivity, such that the sensitivity per unit molecular weight is relatively constant. A similar relationship is roughly applicable to the ribosomal and transfer RNA's when taken as a group, although in this case the sensitivity per unit molecular weight is 50 to 100 fold greater.
A model is proposed in which this marked difference in actinomycin sensitivity arises as a consequence of the transcription of stretches of contiguous repetitive genes by RNA polymerase molecules which attach to the DNA only at a limited number of entry points, the highest probability of attachment being at the beginning of a stretch.
506 citations
TL;DR: It appears that the reduced protein synthesis during mitosis results from a lowered rate of attachment of ribosomes to messenger RNA and initiation of polypeptide synthesis.
443 citations
TL;DR: It is concluded that the RNA polymerases are specifically localized within the nucleus and may, therefore, play specific roles in the regulation of genetic transcription.
Abstract: The DNA-dependent RNA polymerase activity present in rat liver nuclei has been solubilized and purified from whole nuclei and from subnuclear fractions. As reported earlier (Roeder, R. G., and W. J. Rutter, Nature, 224, 234 (1969)), two major chromatographically distinct enzymatic species (I and II) are present in whole nuclei. Subfractionation of whole nuclei into nucleolar and nucleoplasmic fractions had little effect on the total recovery of activity. Purified nucleoli contain predominantly polymerase I, whereas the nucleoplasmic fraction is greatly enriched for polymerase II. A third minor peak of activity has also been resolved in the nucleoplasmic preparations. We conclude that the RNA polymerases are specifically localized within the nucleus and may, therefore, play specific roles in the regulation of genetic transcription.
417 citations
TL;DR: The virions of vesicular stomatitis virus contain an enzyme that catalyzes the incorporation of ribonucleotides into RNA, and the product of the reaction is mainly RNA complementary in base sequence to that of veS virus RNA.
Abstract: The virions of vesicular stomatitis virus contain an enzyme that catalyzes the incorporation of ribonucleotides into RNA. The product of the reaction is mainly RNA complementary in base sequence to that of vesicular stomatitis virus RNA.
365 citations
TL;DR: A number of possible explanations for the greater sensitivity of DNA synthesis and the sequential inhibition of DNA, RNA and protein synthesis at higher concentrations are suggested.
Abstract: The inhibitory effects of anti-tumor, bacterial filament forming platinum compounds, Cis-Pt(II) (NH3)2Cl2 (A), Cis-Pt(IV) (NH3)2Cl4 (B), and Pt(II) (NH2)2(CH2)2Cl2(C) on DNA, RNA and protein syntheses was measured by the incorporation of 3H-thymidine, 3H-uridine, and 3H-L-leucine, respectively, into an acid-insoluble polymer in human amnion AV3 cells. Compound A, the most effective tumor-inhibiting platinum compound, was shown to selectively inhibit DNA synthesis below 5μM and to inhibit 3H-thymidine incorporation more rapidly than 3H-uridine or 3H-leucine incorporation at 25μM. Like A, compounds B and C were also shown to inhibit all three processes after a 24-hour period of treatment at 25μM. A correlation was established between the relative anti-tumor effectiveness of compounds A, B, and C and the extent of their inhibitory effects. On the other hand, two non-tumor-inhibiting platinum compounds, [Pt(II) (NH3)4]Cl2 (D) and Trans-Pt(IV) (NH3)2Cl4 (E) had no inhibitory effects, except compound E, which exhibited a rapid initial inhibition of 3H-L-leucine incorporation at 100μM. The inhibition of 3H-thymidine incorporation into cells pretreated 4 h with 5μM of compounds A, B, and C was shown to be irreversible. Finally the inhibition of the incorporation of 3H-thymidine into DNA by A was shown not to be caused by the inhibition of the uptake of the tracer into the acid-soluble pool. A number of possible explanations for the greater sensitivity of DNA synthesis and the sequential inhibition of DNA, RNA and protein synthesis at higher concentrations are suggested.
363 citations
TL;DR: This reaction is sensitive to anisomycin, an inhibitors of mammalian protein synthesis, but is not affected by the bacterial inhibitor chloramphenicol nor by cyclohexamide, an inhibitor of translocation in mammalian systems.
349 citations
TL;DR: The isolation of an adenine-rich polymer from purified messenger RNA obtained from rabbit reticulocyte polysomes is described and its relationship to the size of the ribosomes from which the messenger RNA is derived is described.
Abstract: POLYPURINES have been isolated from subcellular fractions of mouse liver by a method which involves a limited nuclease digestion of the RNA, followed by chromatography of the digestion products on polystyrene columns1–3. These polypurines consist of clusters of adenylic acid and guanylic acid in which the A/G ratio is 2–10; the materials isolated from the rough endoplasmic reticulum have sedimentation coefficients of 3–5S, but a molecule containing twenty nucleotides can be obtained from the free polysomes4. The latter polymer is part of a rapidly labelled RNA species that sediments between the 32S subunit and 5S RNA when EDTA-treated polysomes are centrifuged on a sucrose density gradient. With longer times of labelling with 32P the polymer is also found in association with the 32S subunit. It seems likely that the adenine-rich polymer is found in close association with messenger-like RNA. These obssrvations prompted us to investigate the polypurine content of a better characterized mammalian messenger RNA. Such an RNA is the haemoglobin messenger RNA which has been isolated from rabbit reticulocytes5,6, and purified by polyacrylamide gel electrophoresis7. This species of RNA8 and a similar RNA from mouse reticulocytes9 have been demonstrated to initiate specific globin synthesis in vitro. We now describe the isolation of an adenine-rich polymer from purified messenger RNA obtained from rabbit reticulocyte polysomes and its relationship to the size of the ribosomes from which the messenger RNA is derived.
313 citations
TL;DR: Observations contribute to an understanding of the orotate-mediated prevention of the galactosamine-induced liver damage, and of the role of pyrimidine nucleotides in this experimental hepatitis.
Abstract: The effects of d-galactosamine, d-glucosamine, and 2-deoxy-d-galactose on rat liver uracil nucleotides were studied in vivo. Enzymic and isotope dilution analyses of the UDP-sugars and of uridine phosphates revealed three major, related changes: an accumulation of the respective UDP-sugar derivatives, a marked decrease of UTP, UDP, and UMP, and a subsequent increase of the sum of hepatic uracil nucleotides. The decrease of uridine phosphates was accompanied by diminished contents of UDPG and UDP-galactose. UMP of total liver RNA was not altered significantly. Inhibition of uridylate synthesis by use of 6-azauridine resulted in a suppression of the d-galactosamine-induced stimulation of uridine phosphate synthesis and of the increase in total acid soluble uracil nucleotides. The trapping of uridine phosphates by formation of UDP-sugar derivatives was most pronounced and most prolonged after administration of d-galactosamine. The uridine phosphate content was lowered to less than 10% of normal within three hours, while the sum of uracil nucleotides increased by 0.35 μmole x g liver−1 x hour−1, from an initial value of 1.24 μmole/g. The quantitative analysis of the time dependent changes of UDP-hexosamines, UDP-N-acetylhexosamines, UDPG, and UDP-galactose revealed a pronounced alteration by d-galactosamine of the UDP-sugar pattern.
Corresponding changes in the distribution of liver uracil nucleotides were obtained after administration of d-glucosamine and 2-deoxy-d-galactose. Both, however, are ineffective in provoking hepatitis. In contrast to d-galactosamine, d-glucosamine and 2-deoxy-d-galactose do not lead to the formation of UDP-hexosamines; furthermore they are less efficient in trapping uridine phosphates in vivo. These observations contribute to an understanding of the orotate-mediated prevention of the galactosamine-induced liver damage, and of the role of pyrimidine nucleotides in this experimental hepatitis.
293 citations
TL;DR: Several RNA tumour viruses contain an enzyme that synthesizes a DNA–RNA hybrid using the single stranded viral RNA as template, and hybridization experiments confirm that the DNA strand is complementary to the viral RNA.
Abstract: Several RNA tumour viruses contain an enzyme that synthesizes a DNA–RNA hybrid using the single stranded viral RNA as template. Hybridization experiments confirm that the DNA strand is complementary to the viral RNA.
261 citations
TL;DR: It is shown that in Drosophila hydei the ribosomal cistrons are located within the nucleolus and in Rhynchosciara hollaenderi and Sciara coprophila, DNA coding for Ribosomal RNA is present both in theucleolus organizer regions of the chromosomes and in micronucleoli scattered throughout the nucleus.
Abstract: Molecular hybridization of radioactive ribosomal RNA with the DNA of cytological preparations is used to study the distribution of the ribosomal cistrons within the polytene chromosomes of three species of Diptera. It is shown that in Drosophila hydei the ribosomal cistrons are located within the nucleolus. In Rhynchosciara hollaenderi and Sciara coprophila, DNA coding for ribosomal RNA is present both in the nucleolus organizer regions of the chromosomes and in micronucleoli scattered throughout the nucleus. The DNA puffs in the salivary chromosomes of these sciarid flies do not contain detectable quantities of ribosomal cistrons. — RNA prepared by in vitro transcription has also been used to localize the ribosomal cistrons in Rhynchosciara. — Modifications in the technique of cytological hybridization are discussed.
TL;DR: Chemical analysis and electron microscopy show that isopycnic centrifugation in discontinuous sucrose density gradients separates smooth and rough cytoplasmic membranes of HeLa cells, and results after addition of guanidine to infected cells support the hypothesis that viral RNA synthesis is initiated in a complex associated with smooth membranes.
TL;DR: Seven polypeptides, varying in size from 24,300 to 92,000 daltons, have been obtained from the WSN strain of influenza virus, and two of them are resistant to degradative enzymes but can be made susceptible to them by treating the particle with phospholipase C.
TL;DR: An RNA dependent DNA polymerase analogous to that of RNA tumour viruses has been found in lymphoblasts of leukaemic patients but not of normal donors.
Abstract: An RNA dependent DNA polymerase analogous to that of RNA tumour viruses has been found in lymphoblasts of leukaemic patients but not of normal donors. The enzyme can use an RNA template from mammalian cells to synthesize DNA.
TL;DR: The results suggest that messenger RNA and nuclear heterogeneous RNA are synthesized separately, and that the transcription of messenger RNA is inhibited by the drug.
Abstract: Cordycepin (3′-deoxyadenosine) suppresses the labeling of messenger RNA in HeLa cells. The drug has no effect on either the labeling of nuclear heterogeneous RNA or on the transport of messenger RNA into the cytoplasm. The results suggest that messenger RNA and nuclear heterogeneous RNA are synthesized separately, and that the transcription of messenger RNA is inhibited by the drug.
TL;DR: The 60–70S RNAs of several transforming and nontransforming avian tumor viruses have different electrophoretic mobilities and it is suggested that the presence of the class a subunit is related to the transforming ability for fibroblasts of the virus.
Abstract: The 60-70S RNAs of several transforming and nontransforming avian tumor viruses have different electrophoretic mobilities. The RNA of transforming viruses contains two electrophoretically separable subunit classes: a and b. The relative concentrations of these subunits vary with the virus strain. Avian leukosis viruses and nontransforming derivatives of a sarcoma virus lack subunits of class a. It is suggested that the presence of the class a subunit is related to the transforming ability for fibroblasts of the virus.
TL;DR: It is concluded that the EMC-RNA is acting as a message for viral proteins in the ascites cell-free system, and is particularly sensitive to the inhibitors cycloheximide and dextran sulphate.
Abstract: 1
A cell-free system from mouse Krebs II ascites cells is described which responds by increased amino acid incorporation into protein on addition of encephalomyocarditis virus (EMC-RNA). RNA from other sources does not produce this response.
2
The stimulation by EMC-RNA occurs over a narrow range of Mg2+ concentrations and is maximal at 5 mM, which is optimal for the endogenous incorporation and lower than that required in the presence of poly(U).
3
The EMC-RNA-directed product is distinguished from the endogenous products by its size and composition.
4
After an initial lag of 4 min, during which the nascent chains are too short to be acid-insoluble, EMC-RNA-directed protein synthesis is active for more than 1 h.
5
EMC-RNA-directed synthesis is particularly sensitive to the inhibitors cycloheximide and dextran sulphate. Using the latter, it has been shown that the initiation of protein synthesis is completed during the first 15 min of incubation.
6
Only 20–30% of the product of the cell-free system, whether endogenous or EMC-RNA-directed, is released from the ribosomes. Despite the size of the viral RNA, it did not appear to promote the formation of exceptionally large polysomes.
7
It is concluded that the EMC-RNA is acting as a message for viral proteins in the ascites cell-free system.
TL;DR: The present data suggest that 36 s and 24 s molecules may be generated when the order of cleavage steps is altered, although their possible role in normal processing cannot be completely excluded.
TL;DR: It is shown that formaldehyde-treated RNA initiates synthesis as well of at least three polypeptides which do not correspond to any known f2 genes, implying that there are several nucleotide sequences on f2 RNA which could initiate protein synthesis but are normally prevented from doing so by the RNA structure.
TL;DR: The finding of multiple pieces of messenger RNA, all smaller than 40 S virion RNA, suggests that VSV polypeptides are synthesized from individual molecules of RNA, rather than from one large messenger RNA.
TL;DR: An improved purification procedure yielded bluetongue virus free from any single-stranded ribonucleic acid (RNA) component, and the denaturation of the genome and separation of the resulting fragments are discussed.
Abstract: An improved purification procedure yielded bluetongue virus free from any single-stranded ribonucleic acid (RNA) component. Double-stranded RNA obtained from purified virus or isolated from infected cells was fractionated into 5 components by means of sucrose gradient sedimentation analysis, and into 10 components by electrophoresis on polyacrylamide gels. The size of these components vary from 0.5 × 106 to 2.8 × 106 daltons, with a total molecular weight estimate of about 1.5 × 107 for the viral nucleic acid. The denaturation of the genome and separation of the resulting fragments are also discussed.
TL;DR: The kinetics of synthesis of capsid polypeptides was studied as a function of the multiplicity of infection and the temperature of incubation and the effect of reovirus infection on host protein synthesis was determined; hostprotein synthesis does not decrease until late during the infection cycle.
TL;DR: The results of reconstruction experiments suggest that the viral 4 S RNA is not simply a contaminant derived from cellular debris, and are in accord with previous suggestions that RNA tumor viruses contain tRNA acquired from the host cell during assembly.
Journal Article•
TL;DR: At a level which was effective as a skin tumor promoter, croton oil increased the rate of incorporation of tritiated precursors into mouse skin macromolecules and stimulation of RNA synthesis may be important in the process of promotion.
Abstract: At a level which was effective as a skin tumor promoter, croton oil increased the rate of incorporation of tritiated precursors into mouse skin macromolecules. After a single application of croton oil, the early 2- to 3-fold stimulation of RNA and protein synthesis and the 60% inhibition of DNA synthesis was followed by a 3-fold stimulation of DNA synthesis at 18 hr. The rates of macromolecular synthesis returned to normal levels within 7 days. A single application of cantharidin, a weak tumor promoter, stimulated both DNA and RNA synthesis in mouse skin. Treatment with either croton oil or cantharidin stimulated the synthesis of rapidly labeled RNA when measured 2 hr after treatment; stimulation of RNA synthesis may be important in the process of promotion. When an incision was made in initiated skin, tumors developed along the line of wound healing. Because croton oil, cantharidin, and other promoters cause hyperplasia and because wound healing causes a local stimulation of mitosis, a stimulation of cell division may be involved in promotion. A possible molecular mechanism of skin carcinogenesis is discussed.
TL;DR: The 5S RNA genes are placed within the region 56E-F of the right arm of chromosome 2 of Drosophila melanogaster, and their localization was determined from autoradiographs, where the radioactivity from hybrids of [3H]RNA and DNA was confined to the 56E -F segment.
Abstract: [ 3H ] RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [ 3H ] uridine. Purified tritiated 5 S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5 S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [ 3H ] RNA and DNA was confined to the 56E-F segment.
TL;DR: A method is described which permits one to localize, at the microscopical level, molecular hybrids formed between a purified 3H-labelled RNA species and DNA in the cell structures of tissue sections.
Abstract: WE describe here a method for DNA–RNA hybridization which permits one to localize, at the microscopical level, molecular hybrids formed between a purified 3H-labelled RNA species and DNA in the cell structures of tissue sections.
TL;DR: The RNA replicating enzyme induced by RNA phage Qβ consists of a single phage specific and three host specific polypeptide chains, and none are known subunits of E. coli DNA-dependent RNA polymerase.
Abstract: The RNA replicating enzyme induced by RNA phage Qβ consists of a single phage specific and three host specific polypeptide chains. At least one of the host subunits is shown to be essential for enzymatic activity, and none are known subunits of E. coli DNA-dependent RNA polymerase.
TL;DR: Six RNA viruses have now been shown to contain DNA polymerase activities directed by single-stranded RNA, double-Stranded RNA and double-stranding DNA, and it is further demonstrated that DNA–RNA hybrids, such as synthetic dC.rG, act as even more effective templates.
Abstract: Six RNA viruses have now been shown to contain DNA polymerase activities directed by single-stranded RNA, double-stranded RNA and double-stranded DNA. It is further demonstrated that DNA–RNA hybrids, such as synthetic dC.rG, act as even more effective templates.
TL;DR: The arrangement of species based on ribosomal RNA homologies agrees in most cases with current taxonomic groupings.
Abstract: Evolutionary divergence among species of the yeast genus Saccharomyces was estimated from measurements of deoxyribonucleic acid (DNA)/DNA and ribosomal ribonucleic acid (RNA)/DNA homology. Much diversity was found in the DNA base sequences with several species showing little or no homology to the three reference species, S. cerevisiae, S. lactis, and S. fragilis. These three reference species also showed little or no homology to each other. On the other hand the diversity among ribosomal RNA base sequences was small since most species showed a high degree of homology to the reference species. The arrangement of species based on ribosomal RNA homologies agrees in most cases with current taxonomic groupings. A yeast hybrid (S. fragilis × S. lactis) was shown to contain two nonhomologous genomes. A minimum genome size of 9.2 × 109 daltons for S. cerevisiae was calculated from the rate of DNA renaturation.