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PubMed1980

Solid-phase synthesis of polynucleotides. III. Synthesis of polynucleotides with defined sequences by the block coupling phosphotriester method.

Preparation of the three hexadecanucleotides, dGpTpApTpCpApCpGpApGpGpCpCpCpTpT, dCpGpApCpGpApGpCpGpTpGpApCpApCpC and cTpGpCpCpGpGpCpCpApCpGpApTpGpCpG, is described by a rapid and simple solid-phase method on polyacrylamide supports. The synthesis were performed by the extension of the method described in the previous paper using di and trinucleotides of defined sequences as an incoming 3'-phosphodiester unit. Although the coupling yields to form phosphotriester bonds are slightly lower than those for the homothymidylic acid series, pure polydeoxyribonucleotides of defined sequences can be synthesized without any major difficulty.

Base Sequence↗
PubMed1997

The actions of polynucleotides on effector stage cloned murine T-helper cells differ in each subset and depend on antigen concentration.

Polynucleotides enhance T-helper (Th) cell-mediated humoral immune responses in naive resting Th cells, B cells, and antigen-presenting cells (APC) from unprimed mouse spleen. If polynucleotides augment Th cell functions independent of the activation stage of Th cells, then polynucleotides may cause hyperimmune responses. In this study we examined the effects of polynucleotides on effector-stage murine Th cell clones in vitro. The A.E7 clone (primed with pigeon cytochrome C, origin: B10.A mice) and CDC35 clone (primed with rabbit gamma-globulin, origin: DBA/2 mice) were used as representative type 1 (Th1) and type 2 (Th2) Th cells, respectively. Th clones were stimulated with antigen (Ag) in polynucleotide-supplemented or control cultures in the presence of syngeneic spleen cells (either CD4- or irradiated). The number of antibody (Ab)-secreting cells was counted to measure T-dependent Ab production. Production of interferon-gamma (IFNgamma) for the Th1 clone and interleukin-5 (IL-5) for the Th2 clone were measured. Without Ag stimulation, cytokine production and the number of Ab-secreting cells formed were very low and not altered by polynucleotides. With suboptimal Ag challenges provided by Ag-primed spleen cells, polynucleotides enhanced IFNgamma production by the Th1 clone, while they suppressed Th1 clone-mediated Ab production and IL-5 production by the Th2 clone. Polynucleotides did not alter Th2 clone-mediated Ab production. These actions of polynucleotides appeared to be dose-dependent. With optimal Ag challenges, polynucleotides did not affect our measures of Th cell activation. Polynucleotide action in vitro on effector-stage Th cell clones differed in each Th cell subset and depended on Ag concentration.

Animals↗
PubMed1985

Glutathione plus cytosol- and microsome-mediated binding of 1,2-dichloroethane to polynucleotides.

1,2-[1,2-14C]Dichloroethane was metabolized by rat hepatic microsomes to products that irreversibly bound polynucleotides. The polynucleotides were then enzymatically hydrolyzed and the products separated by a high-performance liquid chromatograph (HPLC) equipped with an ODS or a SCX column. The products of microsome-mediated binding were identified in the HPLC eluate as 1,N6-ethenoadenosine to polyadenylic acid, 3,N4-ethenocytidine to polycytidylic acid, and two cyclic derivatives to polyguanylic acid. 1,2-[1,2-14C]Dichloroethane was also metabolized in the presence of a glutathione (GSH)-cytosolic fraction and a polynucleotide. After enzymatic hydrolysis of the polynucleotide, the major peak of radioactivity was eluted from a Sephadex G-25 column in the salt volume which would exclude the presence of a product containing both GSH and a nucleoside. Chromatography by ODS-HPLC of the major peak from Sephadex G-25 indicated the presence of a GSH metabolite of 1,2-dichloroethane that did not contain a nucleoside. A similar hydrophilic peak was obtained for the hydrolysis products of polynucleotides from a glutathione plus cytosol incubation in which the polynucleotide instead of being added prior to the incubation was added after the incubation. The products of the glutathione plus cytosol metabolism of 1,2-[1,2-14]dichloroethane appear to be glutathione metabolites that coisolated with the polynucleotides rather than covalently bound adducts. In conclusion, covalently bound adducts were identified for microsome-mediated binding of 1,2-dichlorethane to polynucleotides, while no evidence was obtained for glutathione plus cytosol-mediated covalent binding to polynucleotides.

Animals↗
PubMed2004

Characterization of a 5'-polynucleotide kinase/3'-phosphatase from bacteriophage RM378.

A polynucleotide kinase from the thermophilic bacteriophage RM378 that infects the thermophilic eubacterium Rhodothermus marinus was identified, expressed, and purified. This polynucleotide kinase was demonstrated to have a 5'-kinase domain as well as a 3'-phosphohydrolase domain. The RM378 polynucleotide kinase had limited sequence similarity to the 5'-kinase domain of the T4 bacteriophage polynucleotide kinase, but apparent homology was not evident within the 3'-phosphohydrolase domain. The domain order of RM378 polynucleotide kinase was reversed relative to that of the T4 polynucleotide kinase. The RM378 phosphohydrolase domain displayed some sequence similarity with the bacterial poly(A) polymerase family, including an HD motif characteristic of the diverse superfamily of metal-dependent HD phosphohydrolases. The RM378 polynucleotide kinase was biochemically characterized and shown to possess 5'-kinase activity on RNA and single- and double-stranded DNA at elevated temperatures. It also showed phosphohydrolase activity on 2':3'-cyclic adenosine monophosphate. This description of the RM378 polynucleotide kinase, along with the recently described RM378 RNA ligase, suggests that the RM378 bacteriophage has to counter a similar anti-phage mechanism in R. marinus as the one that the T4 phage has to counter in Escherichia coli.

Adenosine Diphosphate↗
PubMed1983

The interaction of estrogen- and antiestrogen-receptor complexes with polynucleotides.

As the polynucleotide domain of the estrogen receptor (Re) is a possible site for the modulation of Re activity, the interaction of antiestrogen (4-hydroxytamoxifen and tamoxifen)-receptor complexes (4-OH-Tam-Re and Tam-Re) with polynucleotides (oligodeoxynucleotide-cellulose, DNA-cellulose, and polyribonucleotide-agarose) was investigated and compared with that of the 17 beta-estradiol-receptor complex (E2-Re). E2-Re- and anti-Re-E2-complexes were optimally bound to oligo(dT)-cellulose and poly(U)-agarose at 0.15 M KCl and pH 7.6. Temperature activation of the Re was not required for these selective interactions to occur, but they were inhibited by 10 mM sodium molybdate. OH-Tam-Re and E2-Re demonstrated similar selectivity for different deoxynucleotide bases [oligo(dG) greater than oligo(dT) greater than or equal than oligo(dC) greater than oligo(dA) greater than or equal to oligo(dI)] and different ribonucleotide bases [poly(G) = poly(I) greater than poly(U) greater than poly(A) greater than or equal to poly(C)]. Quantitatively, Tam-Re bound significantly less to oligo(dT)-cellulose than did OH-Tam-Re, which did not differ significantly from E2-Re, a result probably related to the dissociation of the lower affinity ligand from the Re/oligo(dT)-cellulose during the assay procedure. Unoccupied Re also bound selectively to these synthetic polynucleotides. It is concluded that: 1) selective binding of Re to synthetic polynucleotides is inhibited by 10 mM sodium molybdate; 2) estradiol is not essential for selective binding to synthetic polynucleotides, since unoccupied Re was only slightly less efficiently bound than E2-Re; and 3) selective binding of Re to synthetic polynucleotides was unaffected by the agonist or antagonist properties of the ligand bound at the steroid-binding site. These data suggest that nonsteroidal antiestrogens are unlikely to exert their antagonist activity by modulating the function of the polynucleotide-binding site of Re.

Animals↗
PubMed1976

Interaction of nucleic acids with electrically charged surfaces. II. Conformational changes in double-helical polynucleotides.

The influence of adsorption of double-stranded (ds) DNA, ds RNA and homopolymeric pairs at a mercury electrode on conformation of these polynucleotides was studied. Changes in the polarographic reducibility of polynucleotides, which were followed by means of normal pulse polarography and linear sweep peak voltammetry at the dropping mercury electrode were exploited to indicate conformational changes. It was found that, as a consequence of adsorption of ds polynuclotides on the negatively charged electrode conformational changes similar to denaturation take place in a narrow potential region around -1.2 V (the region U). After sufficiently long time of the contact with the electrode (under our conditions about 10 s) these changes reach limiting values, which can approach total denaturation. Upon adsorption of ds polynucleotides on the electrode charged to more positive potentials than the region U either (1) no conformational changes occur or (2) only a small part of the polynucleotide (probably labile regions of the ds molecule) is very quickly denatured - the remainder of the molecule preserves its ds structure. Conformational changes of adsorbed ds polynucleotides are influenced by factors which change the stability of ds polynucleotides in solution. It is supposed that denaturation of ds polynucleotides in the region U might result from the strains connected with the repulsion of certain segments of the molecule anchored on the electrode from the negatively charged surface.

Animals↗
PubMed1998

Effect of polynucleotides on the inhibition of neutrophil elastase by mucus proteinase inhibitor and alpha 1-proteinase inhibitor.

DNA released from neutrophils at sites of inflammation may modulate tissue proteolysis. We used tRNA and synthetic polynucleotides as models of DNA to study the influence of polynucleotides on the inhibition of neutrophil elastase by its endogenous inhibitors alpha1-proteinase inhibitor (alpha1-PI) and mucus proteinase inhibitor (MPI). Affinity chromatography showed that polynucleotides form electrostatic complexes with elastase and MPI but not with alpha1-PI, the highest affinity being for MPI. The tight-binding partial inhibition of elastase by polynucleotides was used to calculate the Kd of the elastase-polynucleotide complexes which ranged from 4 microM to 21 nM. One mole of tRNA was able to bind 9 mol of elastase. Polydeoxycytosine and tRNA significantly impaired the reversible inhibition of elastase by MPI: they moderately increased the rate of enzyme-inhibitor association, strongly enhanced the rate of complex dissociation, and lowered the enzyme-inhibitor affinity by factors of 34 and 134, respectively. The two polynucleotides also decreased the rate of the irreversible inhibition of elastase by alpha1-PI by factors of 30 and 3, respectively. Polynucleotides also changed the mechanism of inhibition of elastase by the two inhibitors from a one-step inhibition reaction to a two-step binding mechanism. Our data may help explain why proteolysis may occur at sites of inflammation despite the presence of active proteinase inhibitors.

Binding Sites↗
PubMed1977

Effects of polyamines on the degradation of ribonucleic acids by polynucleotide phosphorylase of Micrococcus luteus.

The effects of polyamines on the breakdown of synthetic polynucleotides [poly(A), poly(C), and poly(U)] by polynucleotide phosphorylase [polyribonucleotide: orthophosphate nucleotidyltransferase, EC 2.7.7.8] from Micrococcus luteus have been studied. Although the breakdown of all the synthetic polynucleotides tested was stimulated by polyamines, the degree of stimulation by polyamines was in the order poly(C) greater than poly(A) greater than poly(U) at pH 7.5. However, the difference in degree of stimulation among polynucleotides decreased as the pH or monovalent cation concentration was increased. In the presence of heparin, an inhibitor of polynucleotide phosphorylase hydrolysis of polynucleotides, spermidine clearly stimulated the breakdown of poly(C) and poly(A), while the breakdown of poly(U) was stimulated only slightly by the addition of spermidine. Although binding of [14C]spermine to polynucleotide phosphorylase was observed by gel filtration, the amount of spermine bound to the enzyme was much less than that to RNA.

Binding Sites↗
PubMedDate not supplied

[Interaction of tripeptides containing arginine and tyrosine (or phenylalanine) residues with synthetic polynucleotides and DNA of various origins].

Model peptides--L-Arg-Gly-L-Arg, L-Arg-L-Tyr-L-Arg and L-Arg-L-Phe-L-Arg bind to different DNAs and synthetic polynucleotides and are found in the major groove of the double helix. Polynucleotide complexes containing L-Arg-Gly-L-Arg were studied in order to consider the influence of the arginine residues on the polynucleotide melting temperature. It was shown, that L-Arg-L-Tyr-L-Arg and L-Arg-L-Phe--L-Arg lowers the melting temperature in all polynucleotides studied. The dependence of the melting temperature of polynucleotide (DNA)--L-Arg-L-Tyr(L-Phe)-L-Arg complexes upon the polynucleotide GC-content has been detected. These effects reflect the intercalation of peptide tyrosyl (or phenylalanyl) residues into the double-stranded polynucleotide.

Arginine↗