Showing papers on "Transcription (biology) 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: 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: 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.
240 citations
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.
235 citations
214 citations
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.
206 citations
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.
186 citations
183 citations
TL;DR: In vitro study revealed the inhibition of DNA-dependent RNA polymeraso activity in the nucleolar preparation isolated from rats treated with cycloheximide but little inhibition was noted for the activity of the extranucleolar nuclear fraction from the same sources.
154 citations
TL;DR: Kinetic and pulse-chase studies indicate that the different-sized products are synthesized simultaneously but at rates which are in the order: small > medium > large.
Abstract: Digestion of purified reovirus type 3 with chymotrypsin degrades 70% of the viral protein and converts the virions to subviral particles (SVP). The SVP contain 3 of the 6 viral structural proteins and all 10 double-stranded ribonucleic acid (RNA) genome segments but not adenine-rich, single-stranded RNA. An RNA polymerase which is structurally associated with SVP transcribes one strand of each genome segment by a conservative mechanism in vitro. The single-stranded products include large (1.2 × 10 6 daltons), medium (0.7 × 10 6 daltons), and small (0.4 × 10 6 daltons) molecules which hybridize exclusively with the corresponding genome segments. The enzyme obtained by heating virions at 60 C synthesizes similar products. Kinetic and pulse-chase studies indicate that the different-sized products are synthesized simultaneously but at rates which are in the order: small > medium > large. Images
TL;DR: Vaccinia virus cores catalyze the incorporation of ATP into polyriboadenylic acid sequences of approximately 150 nucleotides in length, and evidence is presented for a covalent association between the poly A sequences and the regular viral RNA moiety.
TL;DR: A transcription factor, Ψr, which preferentially stimulates the synthesis of ribosomal RNA in vitro has been identified in crude extracts of E. coli and is also a component of Qβ replicase.
Abstract: A transcription factor, Ψ r , which preferentially stimulates the synthesis of ribosomal RNA in vitro has been identified in crude extracts of E. coli. This factor activity is also a component of Qβ replicase.
TL;DR: Results are consistent with the idea that there is a site between genes Q and S that is necessary for expression of the late genes both in the right and in the left arms of the mature λ DNA molecule, at least in the prophage state.
TL;DR: It is suggested that both the true-late and the quasi-late messengers may be active in protein synthesis at 20 minutes and that the “turn-off” of early protein synthesis may be due to control at the level of transcription rather than a mechanism involving translational control.
TL;DR: In the presence of σ, E. coli RNA polymerase forms rifampicin resistant complexes with DNA in the absence of nucleoside triphosphates, so the number of ρ-recognized promoters per genome for several DNA phages could be determined.
Abstract: In the presence of σ, E. coli RNA polymerase forms rifampicin resistant complexes with DNA in the absence of nucleoside triphosphates. These complexes only form at promoter sites, so the number of σ-recognized promoters per genome for several DNA phages could be determined.
TL;DR: Observations indicate that transcription of certain early functions can occur from the parental genome but the integration of late functions within virus membranes is essential for the completion of maturation.
TL;DR: The membrane filter experiments in conjunction with the kinetics experiments suggest that when RNA polymerase, DNA and the purine triphosphates are mixed in a low salt medium, an initiation complex is formed at a specific site on T7 DNA and that the complex does not dissociate at high salt.
TL;DR: MOST inhibitors of RNA synthesis act on the DNA template rather than directly on the polymerizing enzyme, so the bacterial polymerase but not the animal polymerase is inhibited by the rifamycins11, streptovaricin12 and probably streptolydigin13.
Abstract: MOST inhibitors of RNA synthesis act on the DNA template rather than directly on the polymerizing enzyme. Antibiotics that inhibit RNA synthesis by binding to DNA include actinomycin D1, miracil D2, nogalomycin3, chromomycin A34, aflatoxin5, echinomycin, daunomycin, mithramycin and olivomycin6, ethidium bromide7, pro-flavine8, nitrogen mustard9 and acetylaminofluorene10. In each case tested, there is evidence that the antibiotic can inhibit RNA synthesis in both animal and bacterial cells, a finding to be expected because the site of the inhibitory action is the DNA template and not the enzyme. On the other hand, a few antibiotics are known to react with the enzyme molecule itself and these are more species selective. The bacterial polymerase but not the animal polymerase is inhibited by the rifamycins11, streptovaricin12 and probably streptolydigin13. Rifamycin has been shown to bind stoichiometrically to the bacterial enzyme molecule and to prevent initiation14, whereas streptolydigin appears to inhibit chain elongation13.
TL;DR: The hydrodynamic properties and the components of membrane-associated virus-specific structures isolated from the cytoplasm of poliovirus-infected HeLa cells have been determined and suggest a model for the membrane- associated replication and translation of viral RNA.
TL;DR: This finding suggests that regulation of the frequency of transcription initiations and/or the yield of enzyme molecules per messenger are responsible for the variable rates of enzyme synthesis which maintain constant enzyme-specific activities.
TL;DR: A soluble RNA-dependent DNA polymerase activity has been released from murine leukemia particles in the presence of manganese and high detergent concentrations.
Abstract: The RNA-dependent DNA polymerase(s) in murine leukemia, murine mammary tumor, and avian myeloblastosis viruses require maganese for optimal activity. The transcription of added synthetic polyribonucleotides is greatly enhanced when manganese is used in place of magnesium. A soluble RNA-dependent DNA polymerase activity has been released from murine leukemia particles in the presence of manganese and high detergent concentrations. Two RNA viruses, visna virus of sheep and a primate syncytial virus, not known to have tumor-producing ability, also contain the polymerase.
TL;DR: The binary complex between RNA polymerase containing sigma factor and sigma specific DNA is more rapidly inactivated during prolonged incubation with rifampicin than a complex formed with unspecific DNA or in the absence of sigma.
Abstract: Addition of rifampicin to a preincubated mixture of RNA polymerase and DNA does not lead to inhibition of the subsequent initiation of RNA chain synthesis. The formation of the enzymatically active binary complex between RNA polymerase and DNA, however, proved to be very sensitive to the action of the inhibitor. Once the complex has formed in the absence of substrate the enzyme is resistant to the antibiotic. The presence of sigma factor is not required for the formation of the resistant complex. In the presence of sigma, however, more resistant complex is formed between enzyme and DNA containing sigma specific initiation sites. The binary complex between RNA polymerase containing sigma factor and sigma specific DNA is more rapidly inactivated during prolonged incubation with rifampicin than a complex formed with unspecific DNA or in the absence of sigma. Rifampicin may therefore be used as a tool to discriminate sigma specific and unspecific active complexes of RNA polymerase and template.
TL;DR: The time course of viral RNA synthesis in influenza-infected cells has been followed by hybridizing the pulse-labeled RNA with a surplus of either unlabeled viral plus or minus strand RNA, which precedes that of plus strand RNA.
TL;DR: The results of both zonal and equilibrium centrifugation indicate that nascent chains of DNA are associated with the 70S viral RNA, and it is concluded that at least two enzymatic activities are under study: transcription of DNA from viral RNA and subsequent, additional synthesis of DNA.
Abstract: Deoxyribonucleic acid (DNA) polymerase activity can be elicited in purified preparations of avian myeloblastosis virus and Rous sarcoma virus (Schmidt-Ruppin strain) by treatment with nonionic detergent. The enzyme(s) and its synthetic products appear to be virion-associated. Enzymatic activity can be inhibited by pretreatment with either ribonuclease (8- to 10-fold inhibition) or actinomycin D (twofold inhibition). By contrast, rifampin has little, if any effect. The enzyme(s) synthesizes two primary products, a ribonucleic acid (RNA):DNA hybrid and DNA which is free of RNA. The results of both zonal and equilibrium centrifugation indicate that nascent chains of DNA are associated with the 70S viral RNA. It is concluded that at least two enzymatic activities are under study: transcription of DNA from viral RNA, and subsequent, additional synthesis of DNA, utilizing product of the initial reaction as template.
TL;DR: A sigma specificity factor induced by infection with bacteriophage T4 directs the in vitro synthesis of RNA species corresponding to those switched on in vivo about 2 min after infection.
Abstract: A sigma specificity factor induced by infection with bacteriophage T4 directs the in vitro synthesis of RNA species corresponding to those switched on in vivo about 2 min after infection.
TL;DR: The RNA polymerase coded by phage T7 specifically transcribes the late regions of T7 DNA in vitro.
Abstract: The RNA polymerase coded by phage T7 specifically transcribes the late regions of T7 DNA in vitro.
TL;DR: It is proposed that cellular senescence could be attributed to an accumulation of errors in the protein synthesizing machinery of cells, and slight alterations in the structure of enzyme proteins involved in biosynthetic pathways might not have any major effect and might, at worst, reduce the metabolic efficiency.
Abstract: ORGEL1 has proposed that cellular senescence could be attributed to an accumulation of errors in the protein synthesizing machinery of cells Slight alterations in the structure of enzyme proteins involved in biosynthetic pathways might not have any major effect and might, at worst, be expected to reduce the metabolic efficiency by a fixed amount2,3 But slight alterations in other enzymes concerned with transcription and translation might be expected to increase the frequency of errors in all proteins of the cell and thus give rise to the ever decreasing metabolic efficiency which is so characteristic of many ageing tissues