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At least 19 recordsLinked to original sources
PubMedDate not supplied

[Comparative antiviral and interferonogenic activity of synthetic polyribonucleotide complexes of poly(I).poly(C) and poly(G).poly(C) in different cell systems].

The antiviral and interferon-inducing activity of synthetic polyribonucleotide complexes poly(I)-poly(C) and poly(G)-poly(C) was studied in chick embryo, mouse embryo and rabbit kidney cell cultures. In chick embryo cell cultures both polyribonucleotides had similar antiviral activities. The interferon-inducing activity was more marked in poly(G)-poly(C) than in poly(I)-poly(C). In the other two cell cultures poly(I)-poly(C) was considerably superior in both activities. The revealed differences in the comparative activity of the polyribonucleotides in relation to the kind of tissue culture were not associated with differences between them in toxicity, sensitivity to pancreatic RN-ase or with possible differences in the duration of the contact with cells necessary for the achievement of the antiviral effect.

Animals↗
PubMedDate not supplied

[Study of the intermolecular association of poly(G).poly(c) and poly(dG).poly(dC) in solutions by methods of 1H to 3H exchange and electron microscopy].

The kinetic of 1H leads to 3H exchange between water and C(8)H-groups of the guanylic residues in poly(G) . poly(C) and poly(dG) . poly(dC) was investigated within the temperature range from 30 to 90 degrees in 0.5 M NaCl (pH 7.2). It was shown that the exchange in freshly dissolved preparations at temperatures lower than 50 degrees proceeds faster than that in the case of GMP. According to the ylide mechanism of the exchange reaction the observed acceleration of the exchange is considered as a consequence of associates formation in poly(G) . poly(c) and poly(dG) . poly(dC) solutions at temperatures lower than 50 degrees. Associates are stabilized by intermolecular hydrogen bonds in which N(7) atoms of guanylic residues take part. The increase of the temperature is accompanied by gradual disappearance of the exchange acceleration. The retardation of exchange, which is characteristic of most non-associated double-stranded polynucleotides and nucleic acids is observed at the temperatures above 60 degrees. The retardation points to thermal destruction of the associates at temperatures higher than 50 degrees. The associates which are characterized by ordered structure including several "side by side" arranged double-stranded molecules were observed by electron microscopy. The addition of EDTA to solutions as well as the increase of temperature leads to destruction of the associates whereas the addition of Mg2+ makes the associates more stable.

Chemical Phenomena↗
PubMed1976

Preparation and properties of an analogue of poly(A) and poly(G): poly(isoguanylic acid).

Isoguanosine-5'-pyrosphosphate, in the presence of an oligonucleotide primer, was polymerized by Escherichia coli polynucleotide phosphorylase under conditions analogous to those required for polymerization of 5'-GMP. The resulting poly(isoguanylic acid), poly(isoG), was a multistranded helix with a stability considerably higher than that of poly(G), and fully resistant to various nucleolytic enzymes. The polymer exhibited a two-step temperature transition profile in moderately alkaline propylene glycol. Alkaline titration in aqueous medium, by ultraviolet and circular dichroism spectroscopy, showed two clearly defined transitions, the second of which was fully cooperative. The accompanying changes in sedimentation constants were consistent with a structure for poly(isoG) of a fourstranded helix, like neutral poly(G). In acid medium, spectral and potentiometric titrations demonstrated the existence of more than one transition in the pH range 6-12, with accompanying protonation of the isoguanosine residues. In neutral medium the polymer formed no complexes with other potentially complementary homopolymers. In acid medium, on the other hand, the protonated form of poly(isoG) did form a triple-stranded complex with poly(I), viz. 2poly(I) . poly(isoG)+. Possible structures are formulated for the neural and protonated forms of poly(isoG) which account for the two-step thermal transition in alkaline propylene glycol and on alkaline titration in aqueous medium. The nature of the protonated form, and its complex with poly(I) is also discussed.

Binding Sites↗
PubMedDate not supplied

[Comparative study of the toxicity of poly G-poly C and poly I-poly C in different objects].

The poly(G).poly(C) complex has the same interferon-inducing and antiviral activity upon parenteral administration to white mice as poly(I).poly(C), but is considerably less toxic. Upon intravenous inoculation of poly(I).poly(C) to mice its LD50 is 15.8 mg/kg whereas poly(G).poly(C) is not toxic in doses up to 200 mg/kg. In rabbits inoculated with poly(I).ploy(C) intravenously its LD50 is 0.22 mg/kg, while poly(G).poly(C) is not toxic in doses of 1 mg/kg. Histological examinations of different organs of mice and rats revealed no pathomorphological changes after a single intravenous and intraperitoneal inoculation of poly(G).poly(C). It exerted no embryotoxic effect in mice in a dose of 5 mg/kg and was considerably less toxic than poly(I).poly(C) in continuous diploid cell cultures of human embryo lung cells.

Animals↗
PubMedDate not supplied

[Laboratory and clinical study of biological activity of poly G-poly C complex].

Poly(G).poly(C) inoculated intravenously to mice in a dose of 100 microgram induced interferon in the blood in amounts comparable to those induced by poly(I).poly (C). In contrast to rapid accumulation (within 2 hours after induction) and rapid disappearance of interferon in response to poly(I).poly(C) inoculation, the interferon induced by poly(G).poly(C) reached the maximum titer by 6 hours and remained at a high level for 24 hours after inoculation. When given to human volunteers intranasally in a dose of 6 mg, the poly(G).poly(C) complex induced interferon in the blood serum in 70% of the subjects in a titer of 85 units/ml within 24 hours.

Administration, Intranasal↗
PubMed1976

Specific positions involved in enzyme catalyzed covalent binding of benzo[a]pyrene to poly(G).

Covalent binding of benzo[a]pyrene to poly(G) was studied with the use of a radioactive assay and specifically labeled substrates to define the role of the 1, 3- and 6-positions of the hydrocarbon during this process. Binding was shown to be dependent on microsomes, NADPH, O2 and poly(G). 7, 8-Benzoflavone and 2', 2'-diethylaminoethyl-2, 2-diphenyl valerate were inhibitory w.hereas modulators of epoxide hydrase activity had little effect. 3H and 14C studies suggested a possible loss of one to two protons. Incorporation of [6-3H1]benzo[a]pyrene provided evidence that the 6-position of the hydrocarbon was not metabolized during covalent attachment to poly(G) and, furthermore, results with [1, 3, 6-3H]benzo[a]pyrene suggest that the 1- and 3-positions may not be involved either. After scaling up of the standard assay 20-fold, characterization of the tritiated BaP-poly(G) complex was carried out by hydrolysis and subsequent chromatography. Thin-layer chromatography of the isolated hydrolysis products treated with HCl or alkaline phosphatase indicated that the complex formed between BaP and poly(G) was covalently linked and composed of hydrocarbon-nucleotide(s).

Animals↗
PubMed1976

Protonated polynucleotide structures. 18. Interaction of oligocytidylates with poly (G).

The faculty for and degree of oligo(C)-poly(G) interaction is described as an essentially chain length - sensitive phenomenon. At neutral pH under suitable experimental conditions, oligocytidylates of chain length greater than four associate with poly(G) to form double-stranded structures, as does poly(C). The extent of complex formation increases with degree of polymerization. The complex at acid pH is shown to be triple-stranded, of stoicheometry 2C/1G. The observation of a 2G/1C artifact is discussed.

Binding Sites↗
PubMed1976

Elucidation of hydrocarbon structure in an enzyme-catalyzed benzo[a]pyrene-poly (G) covalent complex.

The carcinogen, benzo[a]pyrene, was covalently attached to poly (G) by liver microsomes from rats pretreated with 3-methylcholanthrene. The complex was hydrolyzed with enzymes or base and products were isolated by Sephadex chromatography. Absorbance and fluorescence spectra of the products fit that of red-shifted pyrene aromatic system and suggest that metabolism has occurred at the 7-, 8-, 9-, and 10-positions of the hydrocarbon. Benzanthracene or chrysene fluorescence were not observed in these preparations. Benzo[a]pyrene derivatives were synthesized and purified by high-pressure liquid chromatography. Dehydration of 7,8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene resulted in the formation of small amounts of 7-oxo-7,8,9,10-tetrahydrobenzoa[a]pyrene. A 7-keto species was also observed after similar treatment of the hydrocarbon-poly(G) hydrolysis products. Evidence of dehydration at the 9,10-positions was not observed. The hydrocarbon covalently bound to poly(G) is, therefore, a derivative of 7,8-dihydroxy-7,8,9,10-tetrahydrobenzol[a]pyrene with nucleic acid substitution at C-10 or 9.

Benzopyrenes↗
PubMedDate not supplied

[Effect of synthetic polynucleotides and RNA on poly(C)-dependent poly(G) polymerase activity of Q beta replicase].

The effect of synthetic polynucleotides and phage RNA on poly(C)-dependent synthesis of poly (G) by Qbeta replicase is studied. It is shown that single stranded poly(U) and poly (dT) are strong inhibitors whereas structured polynucleotides poly(A), MS2 RNA as well as double stranded complexes poly(A)-poly(U) and poly(A)-poly(dT) do not affect the synthesis of poly(G). It is suggested that contact region of template with enzyme has single stranded unhelical structure and affinity of polynucleotides to Qbeta replicase is determined by degree of their secondary structure.

Kinetics↗
PubMed1975

Double-stranded complex of polyguanylic and polycytidylic acids and its antiviral activity in tissue culture.

The antiviral activity and conditions of formation of the most active double-stranded complexes of synthetic homopolynucleotides, polyriboguanylic and polyribocytidylic acids, were studied on the model of primary trypsinized chick embryo cells and RNA-containing viruses. The (poly G).(poly C) complex was very active against the viruses tested; their replication in cell cultures was inhibited completely. The antiviral activity of the (poly G).(poly C) complex increased markedly in the presence of diethylaminoethyl- (DEAE-) dextran. After treatment with 1 mug/ml of (poly G). (poly C) for 1 hour in the presence of 100 mug/ml DEAE-dextran, the cell sheet remained protected for 5-7 days. Preparations of (poly G).(poly C) obtained under optimal conditions were as active as (poly I).(poly C) complexes and exceeded them markedly in the level of the therapeutic index which under the present experimental conditions was 5-10 times 10(3) for (poly G).(poly C). Highly purified homopolymers with sufficiently high molecular weight must be used for production of active and stable (poly G).(poly C) complexes.

Animals↗
PubMed1978

[Antiviral activity of the complexes obtained at different ratios of complementary homopolyribonucleotides].

Antiviral activity of the complexes of synthetic polyribonucleotides, i.e. poly (I).poly (C) and poly (G).poly (C) obtained at non-equimolar ratios of homopolymers was studied. The system of chick embryon fibroblasts and horse Venezuellan eguine encephalitis virus served as the model. It was shown that the active and stable complexes poly (I).poly (C) and poly (G).poly (C) were formed at some excess of poly (C), i.e. at the ratio of poly G) or poly (I) to poly (C) equal to 40/60 to 20/80 molar per cent. The role of the excessive poly (C) in formation of the stable secondary structure of the nucleotide complexes and its significance as one of the means for affecting the fine structure of double-stranded RNA were discussed.

Animals↗
PubMedDate not supplied

[Hydrolysis and the inactivation of double-stranded polyribonucleotides by monkey blood serum].

The effect of Macaca rhesus monkey blood serum on double-stranded polyribonucleotide complexes poly (I).poly (C), poly (G).poly (C), and poly (G,I).poly (C) was studied. The poly (I).poly (C) complex was found to be the most sensitive to hydrolysis as indicated by a decrease of the molecular weight, accumulation of acid-soluble products and a sharp decline of the antiviral and interferon-inducing activities in tissue culture after incubation of the complex in the presence of the serum at 37 degrees C for 1 hour. The poly (G).poly (C) complex was the most stable, and retained its original activity in tissue culture and a high molecular weight after 3-hour incubation with the serum. The interferon-inducing activity of all the complexes under study assayed by intravenous injection in a dose of 2 mg to M. rhesus monkeys was similarly low irrespective of their sensitivity to the serum. Conjectural species features of the interferon induction system in monkeys are discussed.

Animals↗
PubMed1978

Differential susceptibilities of DNA polymerases-alpha and -beta to polyanions.

The effects of various polyanions including synthetic polynucleotides on DNApolymerases-alpha and -beta from blastulae of the sea urchin Hemicentrotus pulcherrimus and HeLa cells were studied. Only DNA polymerase-alpha was inhibited by polyanions, such as polyvinyl sufate, dextran sulfate, heparin, poly(G), poly(I), poly(U) and poly(ADP-Rib). Of the various polynucleotides tested, poly(G) and poly(I) were the strongest inhibitors. Kinetic studies showed that the Ki value for poly(G) was 0.3 microgram/ml and that poly(G) had 20-fold higher affinity than activated DNA for the template-primer site of DNA polymerase-alpha. Poly(U) and poly(ADP-Rib) were also inhibitory, but they were one hundredth as inhibitory as poly(G) or poly(I). Poly(A), poly(C), poly(A).poly(U) AND POLY(I).poly(C) were not inhibitory to DNA polymerase-alpha. In contrast, DNA olymerase-beta was not affected at all by these polyanions under the same conditions.

Animals↗
PubMed1977

Comparison of mRNA binding by Met-tRNAf binding protein and mRNA-associated proteins.

One of the heterogeneous mRNA binding activities in the 0.5 M KCl eluate of rabbit reticulocyte polyribosomes co-purified to apparent homogeneity through phosphocellulose and DEAE-cellulose chromatography and isoelectric focusing with the GTP-dependent Met-tRNAf binding protein. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis following iodination revealed putative subunits of 51,000 and 39,000 apparent molecular weights. Specificity of mRNA binding by this protein was suggested since the ability of poly(A)-rich mRNA to compete for binding of [3H]poly(A)-rich mRNA exceeded by 10- to 100-fold that of most natural or synthetic RNAs tested, except for the hybrid poly(G) - poly(C) which was almost as effective, and poly(G), which was more effective, at competing for protein-dependent binding. The mRNA binding activity exhibited complete GTP independence and no apparent divalent cation requirement. GDP inhibited Met-tRNAf binding but neither GDP, GMP, nor 7-methylguanosine 5'-monophosphate inhibited mRNA binding by this protein. Similar data were obtained with respect to the ability of natural or synthetic RNAs to compete for binding of [3H]poly(A)-rich mRNA by proteins associated with purified rabbit reticulocyte polyribosomal mRNA-protein particles; while poly(A) was an ineffective competitor, poly(G) was more effective than even mRNA at competing for protein-dependent binding. No significant binding of Met-tRNAf by mRNA-protein particles was detected. Polyacrylamide gel electrophoresis following reduction of mRNA-protein particles revealed apparent co-migration of a major protein with one subunit of the GTP-dependent Met-tRNAf binding protein, but no protein comparable to the 39,000 dalton subunit protein.

Animals↗
PubMedDate not supplied

[Nitrogen mustard fixes the Z-conformation in poly[d(G-C)]poly[d(G-C)] and DNA].

The reactions of poly(dG-dC).poly(dG-dC) and (dG-dC)10 insert in the plasmid pGC20 with N-methyl-bis(2-chloroethyl)-amine (nitrogen mustard, HN-2) have been studied. It is shown that nitrogen mustard does not induce the B----Z transition in poly(dG-dC).poly(dG-dC), but produces fixation of the polynucleotide Z-conformation once this exists. In the case of pGC20 plasmid DNA, nitrogen mustard also fixes Z-form of the (dG-dC)-insert. The rate constant of the reaction of nitrogen mustard with guanine in the polynucleotide (k = 9,0.10(-3) min-1) is about one-third of that for the fixation of Z-form of the (dG-dC)-insert in the plasmid (k1 = 2,8.10(-2) min-1) which is attributed to a greater rate of formation of diguanyl derivative in the opposite DNA chains. It is suggested that nitrogen mustard is capable of fixing the Z-form DNA not only in vitro, but also in vivo.

Circular Dichroism↗
PubMed1977

Light-induced free radical alkylation of polynucleotides and their enzymatic digestion.

Ultraviolet light-induced free radical alkylation with 2-propanol or D-ribose, initiated with di-tert-butyl peroxide, of poly (G), poly (U20G), and poly(A) led to the substitution of the appropriate group for the H-8 atom of the purines and addition across the 5,6-double bond of the pyrimidines. The alkylated polynucleotides were subjected to nucleolytic digestion with several nucleases. T1-RNase digestion of poly(G) irradiated with 2-propanol gave a mixture of the modified and non-modified mononucleotides. Similarly, pancreatic RNase digestion of the irradiated poly(U20G) resulted in a mixture of the appropriate mononucleotides. A T2-RNase treatment of poly(A) irradiated with 2-propanol gave the modified Ado-21:3'-P, while T2-RNase digestion of poly(A) irradiated with D-ribose led to the cyclic modified mononucleotides, in addition to the modified mononucleotides.

Alkylation↗