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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↗
PubMedDate not supplied

[Effect of thymosin on interferon production and antiviral resistance in mice].

The 5th and 6th fractions of thymosin, a hormone of the thymus gland, stimulated interferon production both in vivo (experiments in white and CBA mice) and in vitro in CBA mouse splenocytes when different interferon inducers were used (phage dsRNA, poly(G): poly(C), NDV, and mitogens). The highest stimulating effect in vivo was observed with interferon induction 6-8 hours after thymosin administration. An increase in production of both alpha/beta and gamma interferons under the influence of thymosin was observed. Thymosin alone induced no interferon synthesis.

Animals↗
PubMed1981

RNA inhibits estrogen receptor binding to DNA.

Cytosol from MTW9 rat mammary tumor contains a high molecular weight inhibitor of estrogen receptor binding to DNA. RNase treatment of crude preparations destroys inhibitory activity, whereas DNase or trypsin treatment are without affect, suggesting that some RNA molecule might be involved; in addition, RNA extracted from tumor cytosol was an effective inhibitor of estrogen receptor binding to DNA. A number of synthetic and natural RNA species were analyzed for inhibitory activity; a definite specificity was observed, with poly(G) > poly(U) > poly(A) or poly(C).

Animals↗
PubMedDate not supplied

[Effect of interferon inducers on the development of specific resistance to tick-borne encephalitis].

Various natural and synthetic interferon inducers stimulate postvaccination immunity to tick-borne encephalitis virus in mice. This capacity was found not only in macromolecular synthetic polyribonucleotides such as (poly I)-(poly C), (poly G)-(poly C), (poly A)-(poly U) and substances with much lower molecular weight such as copolymers of vinylpyrrolidone with maleic anhydride, crotonic acid or metacrylic acid but also in a low molecular interferon inducer tiloron. These and other interferon inducers examined (endotoxin S-typhi, statolon) exhibited no parallelism between the intensity of their stimulating effect of immunogenesis and levels of interferon production induced in mice and the associated resistance to tick-borne encephalitis. The results indicate a possibliity of using various interferon inducers for stimulation of post-vaccination immunity to tick-borne encephalitis.

Animals↗
PubMed2006

Reengineering CCA-adding enzymes to function as (U,G)- or dCdCdA-adding enzymes or poly(C,A) and poly(U,G) polymerases.

CCA-adding enzymes build and repair the 3'-terminal CCA sequence of tRNA. These unusual RNA polymerases use either a ribonucleoprotein template (class I) or pure protein template (class II) to form mock base pairs with the Watson-Crick edges of incoming CTP and ATP. Guided by the class II Bacillus stearothermophilus CCA-adding enzyme structure, we introduced mutations designed to reverse the polarity of hydrogen bonds between the nucleobases and protein template. We were able to transform the CCA-adding enzyme into a (U,G)-adding enzyme that incorporates UTP and GTP instead of CTP and ATP; we transformed the related Aquifex aeolicus CC- and A-adding enzymes into UU- and G-adding enzymes and Escherichia coli poly(A) polymerase into a poly(G) polymerase; and we transformed the B. stearothermophilus CCA-adding enzyme into a poly(C,A) polymerase by mutations in helix J that appear, based on the apoenzyme structure, to sterically limit addition to CCA. We also transformed the B. stearothermophilus CCA-adding enzyme into a dCdCdA-adding enzyme by mutating an arginine that interacts with the incoming ribose 2' hydroxyl. Most importantly, we found that mutations in helix J can affect the specificity of the nucleotide binding site some 20 A away, suggesting that the specificity of both class I and II enzymes may be dictated by an intricate network of hydrogen bonds involving the protein, incoming nucleotide, and 3' end of the tRNA. Collaboration between RNA and protein in the form of a ribonucleoprotein template may help to explain the evolutionary diversity of the nucleotidyltransferase family.

Binding Sites↗
PubMed2003

Isolation of a ribonuclease from fruiting bodies of the wild mushroom Termitomyces globulus.

A ribonuclease, with a molecular mass of 13 kDa and a ubiquitin-like N-terminal sequence, has been isolated from fruiting bodies of the mushroom Termitomyces globulus. The ribonuclease demonstrated ribonucleolytic activity toward poly A, poly C, poly G and poly U, with the activity toward poly A and poly C being much higher than that toward poly G and poly U. The ribonuclease was unadsorbed on DEAE-cellulose but adsorbed on Affi-gel blue gel and CM-Sepharose. The enzyme required a temperature of 70 degrees C for expression of maximal activity. However, the enzyme expressed nearly the same optimal activity over a wide pH range of 5.0-8.0.

Agaricales↗
PubMed1986

Interaction of transition metal ions with Z form poly d(A-C).poly d(G-T) and poly d(A-T) studied by I.R. spectroscopy.

Interactions between Ni2+, Co2+ and purine bases have been studied by I.R. spectroscopy in the case of double stranded regularly alternating purine-pyrimidine polynucleotides poly d(A-T), poly d(A-C).poly d(G-T) and poly d(G-C). The spectra of polynucleotide films have been recorded in hydration and salt content conditions which correspond to the obtention of the classical right-handed (A,B) and left-handed (Z) helical conformations. Selective deuteration of the 8C site of purines has been obtained and is used to detect interactions between the transition metal ions and the adenine or guanine bases. The spectral region between 1500 and 1250 cm-1 corresponding to base in-plane vibrations and involving also the glycosidic linkage torsion is discussed in detail. The selective interaction between the transition metal ion and the 7N site of the purine base is considered to be partly responsible for the stabilization of the base in a syn conformation, which favours the adoption by the polynucleotide (poly d(G-C), poly d(A-C).poly d(G-T) or poly d(A-T)) of a Z type conformation.

Cobalt↗
PubMedDate not supplied

Left-handed helical conformation of poly[d(A-m5C).d(G-T)].

Poly[d(G-C)] serves as the prototype for the right-to-left (B to Z) transition in he helical sense of DNA, both in solution and inthe crystal form. However, the question remains as to which other synthetic and natural DNAs have the potential to adopt left-handed conformations. One logical candidate is the canonical alternating purine-pyrimidine sequence d(A-C)n.d(G-T)n which seems to be widely disseminated in eukaryotic genomes. Our approach to this question is based on the enzymatic synthesis of poly[d(A-C).d(G-U)] derivatives with systematic methyl and halogen substitutions in the C-5 position of the pyrimidines C and U. Such modifications in poly[d(G-C)] have previously been shown to potentiate the B to Z transition. Here we report a highly cooperative, reversible, salt- and temperature-dependent transition for poly[d(A-m5C).d(G-T)], a repeat of the d(A-m5C) sequence which may occur in natural DNA. Spectroscopic studies and the demonstrated ability to bind anti-Z-DNA antibodies suggest that the new helical conformation is left-handed and shares structural features with known Z-DNA. However, a novel property, not exhibited by poly[d(G-C)], is the profound temperature dependence of the conformational equilibrium.

Circular Dichroism↗
PubMed1974

Effects on protein synthesis of injecting synthetic polyribonucleotides into living cells.

Micro-injection into the oocytes and eggs of Xenopus laevis was used to ascertain the effects of synthetic polyribonucleotides on protein synthesis in living cells. Poly(U) and poly(A) were not translated detectably, nor did they change the rate of endogenous protein synthesis. The same was true of poly(G,U), poly(A,G,U), poly(A,C,G,U), G-U-G-(U)(n), A-(U)(n) and AUG. In contrast, A-U-G-(U)(n) was a potent inhibitor of protein synthesis in the cell. This might be because it is initiated normally but lacks a termination codon, or because it inhibits the translation of other molecules in some way not dependent on its normal initiation. Poly(G,U), poly(A,G,U) and poly(A,C,G,U) inhibited haemoglobin synthesis when they were injected into the oocyte with haemoglobin mRNA. The synthetic polyribonucleotides did not inhibit the translation of the natural mRNA when the two sorts of molecules were injected at different times. It is suggested that the synthetic RNA molecules compete with the natural mRNA for a pre-initiation factor in limited supply.

Animals↗
PubMed1989

Hydrophobic moieties in cations, anions, and alcohols promote the B-to-Z transition in poly[d(G-C)] and poly[d(G-m5C)].

Previous results from our laboratory showed that an increase in the nonpolar alkyl chain length in tetraalkylammonium cations is accompanied by greater efficiency in driving the B-to-Z transition. Analogous effects are observed when the hydrocarbon portion of carboxylate anions and alcohols is increased in size. The more hydrophobic species have a greater ordering effect on the aqueous solvent and promote formation of the less hydrated Z-DNA conformer.

Alcohols↗
PubMed1986

1H nuclear magnetic resonance study of the dynamic properties of the B and Z-forms of poly[d(A-br5C).d(G-T)].

Poly[d(A-br5C).d(G-T)], a synthetic polynucleotide with a 50% A-T base composition, undergoes a reversible, highly co-operative transition between the right-handed B and left-handed Z conformations. The latter is stabilized at both elevated temperature and ionic strength. The B and Z-forms of poly[d(A-br5C).d(G-T)] coexist in 4.6 M-NaCl at 45 degrees C. Due to slow exchange, two sets of Tim and Gim resonances are observed and can be assigned to the B and Z conformations (the chemical shifts are, respectively, Tim = 13.4, 14.1 p.p.m. (parts/million); and Gim = 11.9, 12.4 p.p.m.). Measurements of the 1H spin-lattice (R1) and spin-spin (R2) relaxation rates of the exchangeable thymine (Tim) and guanine (Gim) imino protons have been used to probe the internal dynamics of the B and Z-forms of poly[d(A-br5C).d(G-T)] and the mechanism of the B-Z transition. The proton exchange behavior in the B and Z conformations is quite different. At elevated temperature, R1 for both Tim and Gim in the B conformation is dominated by exchange with the solvent, with Tim exchanging more rapidly than Gim. This demonstrates that exchange involves the opening of single base-pairs and that neighboring A-T and G-br5C base-pairs exchange independently of each other. B-form poly[d(A-br5C).d(G-T)] is unusual in that there is an acceleration of the Tim exchange rate with increasing NaCl concentration. Conversion to the Z-form by addition of 4.5 M-NaCl dramatically reduces both the Tim and Gim exchange rates (estimated to be less than 2 s-1 at 70 degrees C). Thus, the G-br5C base-pair and, in particular, the A-T base-pair are stabilized in the Z conformation. By measuring relaxation rates at 45 to 50 degrees C where the B and Z-forms are in equilibrium, we find that the B-Z interconversion rates are less than two per second. In the B conformation at 25 degrees C, the dipolar contributions to the imino proton relaxation rates are about one-third of those expected on the basis of a rigid rod model for 65 base-pair fragments, a difference we assign to large amplitude (30 degrees high frequency (less than 100 ns) out-of-plane motions of the bases. Conversion to the Z conformation has little effect on the dipolar contributions to relaxation, i.e. on the internal motions.(ABSTRACT TRUNCATED AT 400 WORDS)

Magnetic Resonance Spectroscopy↗
PubMedDate not supplied

[Interaction of eukaryotic tyrosyl-tRNA-synthetase with high molecular weight RNA].

The affinity of eukaryotic tyrosyl-tRNA synthetases from bovine liver and from yeast for E. coli ribosomal RNA and synthetic polyribonucleotides has been studied by protein binding on the rRNA-Sepharose column and enzyme inhibition by high molecular weight RNAs. Tyrosyl-tRNA synthetase from bovine liver (Mr 2.59 kDa) was fully retained on the rRNA-Sepharose and eluted by buffer with 100 mM KCl. The functionally active modified form of bovine liver tyrosyl-tRNA synthetase obtained by endogenous limited proteolysis (Mr 2.38 kDa) partially maintains the affinity for rRNA and is eluted by 50 mM KCl. The highest rRNA-binding ability was revealed for yeast tyrosyl-tRNA synthetase eluted by 200 mM KCl. The E. coli tyrosyl-tRNA synthetase was not retained on rRNA-Sepharose. The aminoacylation activities of both bovine liver and yeast tyrosyl-tRNA synthetases were efficiently inhibited by rRNA and the inhibition was partially competitive in respect to tRNA(Tyr). At the same time the activities of proteolytically modified bovine tyrosyl-tRNA synthetase and E. coli tyrosyl-tRNA synthetase were not influenced by the addition of rRNA. Synthetic single- and double-stranded polyribonucleotides specifically inhibited the activity of bovine tyrosyl-tRNA synthetase to different extent. The inhibition degree of bovine liver tyrosyl-tRNA synthetase decreased in the order: poly (G) greater than poly (I) greater than poly (I).poly (C) greater than poly (G).poly (C) greater than poly (C) greater than poly (A). Poly (U) did not inhibit the activity of bovine liver tyrosyl-tRNA synthetase.

Animals↗
PubMed2001

Expression of the Moraxella catarrhalis UspA1 protein undergoes phase variation and is regulated at the transcriptional level.

The UspA1 protein of Moraxella catarrhalis has been shown to function as an adhesin that mediates adherence to human epithelial cell lines in vitro (E. R. Lafontaine, L. D. Cope, C. Aebi, J. L. Latimer, G. H. McCracken, Jr., and E. J. Hansen, J. Bacteriol. 182:1364-1373, 2000). In the present study, cell lysates prepared from individual colonies of several M. catarrhalis wild-type strains were analyzed by Western blot analysis using monoclonal antibodies (MAbs) specific for the UspA1 protein. Expression of UspA1 was shown to exhibit phase variation that was correlated with both adherence ability in vitro and the number of guanine (G) residues contained within a homopolymeric [poly(G)]tract located upstream of the uspA1 open reading frame (ORF). Nucleotide sequence analysis revealed that isolates expressing relatively high levels of UspA1 had 10 G residues in their uspA1 poly(G)tracts, whereas isolates that expressed much lower levels of UspA1 had 9 G residues. This poly(G) tract was located 30 nucleotides (nt) upstream of the uspA1 ORF and 168 nt downstream of the uspA1 transcriptional start site. Primer extension experiments, RNA slot blot analysis, and cat reporter constructs were used to demonstrate that M. catarrhalis isolates with 10 G residues in their uspA1 poly(G) tracts expressed two-to threefold more uspA1 mRNA than did isolates which had 9 G residues in their poly(G)tracts. Northern hybridization analysis revealed that an intact uspA1 mRNA was readily detectable in RNA from M. catarrhalis isolates that had 10 G residues in their uspA1 poly(G) tracts, whereas no full-length uspA1 mRNA was observed in isolates whose poly(G)tracts contained 9 G residues. M. catarrhalis strain O35E uspA1 genes that contained wild-type and mutated poly(G) tracts were expressed in Haemophilus influenzae to demonstrate that the length and composition of the poly(G)tract affected expression of UspA1.

Bacterial Adhesion↗
PubMed2003

The Moraxella catarrhalis immunoglobulin D-binding protein MID has conserved sequences and is regulated by a mechanism corresponding to phase variation.

The prevalence of the Moraxella catarrhalis immunoglobulin D (IgD)-binding outer membrane protein MID and its gene was determined in 91 clinical isolates and in 7 culture collection strains. Eighty-four percent of the clinical Moraxella strains expressed MID-dependent IgD binding. The mid gene was detected in all strains as revealed by homology of the signal peptide sequence and a conserved area in the 3' end of the gene. When MID proteins from five different strains were compared, an identity of 65.3 to 85.0% and a similarity of 71.2 to 89.1% were detected. Gene analyses showed several amino acid repeat motifs in the open reading frames, and MID could be called a putative autotransport protein. Interestingly, homopolymeric [polyguanine [poly(G)]] tracts were detected at the 5' ends within the open reading frames. By flow cytometry, using human IgD and fluorescein isothiocyanate-conjugated anti-IgD polyclonal antibodies, most strains showed two peaks: one high- and one low-intensity peak. All isolates expressing high levels of MID had 1, 2, or 3 triplets of G's in their poly(G) tracts, while strains not expressing MID had 4, 7, 8, or 10 G's in their poly(G) tracts or point mutations causing a putative preterminated translation. Northern blot analysis revealed that the mid gene was regulated at the transcriptional level. Experiments with nonclumping variants of M. catarrhalis proved that bacteria lost their MID expression by removing a G in their poly(G) tracts. Moraxella strains isolated from the nasopharynx or from blood and sputum specimens expressed MID at approximately the same frequency. In addition, no variation was observed between strains of different geographical origins (Australia, Europe, Japan, or the United States). MID and the mid gene were found solely in M. catarrhalis, whereas related Neisseria and Moraxella species did not express MID. Taken together, MID appears to be a conserved protein that can be found in essentially all M. catarrhalis strains. Furthermore, MID is governed by poly(G) tracts when bacteria undergo phase variation.

5' Flanking Region↗
PubMed1994

DNA binding of a spermine derivative: spectroscopic study of anthracene-9-carbonyl-N1-spermine with poly[d(G-C).(d(G-C)] and poly[d(A-T).d(A-T)].

The binding of polyamines, including spermidine (1) and spermine (2), to poly[d(G-C).d(G-C)] was probed using spectroscopic studies of anthracene-9-carbonyl-N1-spermine (3); data from normal absorption, linear dichroism (LD), and circular dichroism (CD) are reported. Ligand LD and CD for transitions located in the DNA region of the spectrum were used. The data show that 3 binds to DNA in a manner characteristic of both its amine and polycyclic aromatic parts. With poly[(dG-dC).(dG-dC)], binding modes are occupied sequentially and different modes correspond to different structural perturbations of the DNA. The most stable binding mode for 3 with poly[d(G-C).d(G-C)] has a site size of 6 +/- 1 bases, and an equilibrium binding constant of (2.2 +/- 1.1) x 10(7) M-1 with the anthracene moiety intercalated. It dominates the spectra from mixing ratios of approximately 133:1 until 6:1 DNA phosphate: 3 is reached. The analogous data for poly[d(A-T).d(A-T)] between mixing ratios 36:1 and 7:1 indicates a site size of 8.3 +/- 1.1 bases and an equilibrium binding constant of (6.6 +/- 3.3) x 10(5) M-1. Thus, 3 binds preferentially to poly[d(G-C).d(G-C)] at these concentrations.

Circular Dichroism↗
PubMed1999

Mutational analysis of the promoter region of the porA gene of Neisseria meningitidis.

The porA gene encodes the class 1 outer membrane protein (OMP1) in Neisseria meningitidis and is under transcriptional control. Promoter regions of porA from different clinical isolates were sequenced and were found to differ in the number of guanosine residues in a poly(G) track located upstream of the -10 region. Isolates that did not express OMP1 had up to nine G residues in the poly(G) track or an adenosine residue within this poly(G) track. Using beta-galactosidase as a reporter gene, the transcriptional activities of the promoter regions of the porA gene from three strains, two of which do not express OMP1, were assayed in both Escherichia coli and N. meningitidis. Mutations in the poly(G) track were created by site-directed mutagenesis and promoter fusions were further analyzed in E. coli and N. meningitidis. The number of nucleotides in the poly(G) track influenced promoter activity: reduction of a poly(G) track of 12nt by one and by two guanosine residues reduced promoter activity. Within the poly(G) track, replacement of an adenosine residue by a guanosine residue increased the promoter activity; replacement of a guanosine residue by an adenosine residue decreased the activity. The similar transcriptional activities for the mutated promoters in E. coli and N. meningitidis are compatible with similar control mechanisms for transcriptional control in both organisms.

Base Sequence↗
PubMed1976

Comparative studies on polyguanylate polymerase and polyadenylate polymerase activities in the DNA-dependent RNA polymerase I fraction from cauliflower.

The properties of poly(G) polymerase and poly(A) polymerase activities in the DNA-dependent RNA polymerase [nucleosidetriphosphate: RNA nucleotidyltransferase EC 2.7.7.6] I fraction from cauliflower (Brassica oleracea var. botrytis) were comparatively investigated. The pH optimum, the effect of ionic strength, the effect of substrate concentration on the rate of synthesis, the effect of divalent metal ion concentration, and the time course of synthesis at different temperatures were all different for the three polymerase activities. The enzyme fraction preferentially utilized denatured DNA. Synthetic poly(C) and poly(U) were more effectively utillized for the synthesis of polyguanylate and polyadenylate, respectively. Further, it was found that poly(G) and poly(A) formed in vitro by the enzyme fraction had chain length of 25-28 and 84-89 nucleotides, respectively, and that poly (adenylate-gluanylate) chain was hardly formed when ATP and GTP were added together as substrates in the same reaction medium.

Adenosine Triphosphate↗
PubMed1988

Inhibition of polypeptide synthesis in cell-free systems by virginiamycin S and erythromycin. Evidence for a common mode of action of type B synergimycins and 14-membered macrolides.

Macrolides, lincosamides and type B synergimycins are powerful inhibitors of protein synthesis in vivo, but many of them were found to be inactive in vitro. In the present work, we confirm that virginiamycin S (a type B synergimycin) and erythromycin (a 14-membered macrolide) have no effect on poly(U)-directed poly(Phe) synthesis. However, the amino-acid polymerization reactions directed by poly(U,G), poly(U,C), poly(A,G) and poly(A,C) were increasingly inhibited (20-50%) by both antibiotics. The action of these inhibitors proved to be template-dependent and favored by the incorporation of proline and of basic amino acids into peptides. Under these conditions, virginiamycin S and erythromycin markedly stimulated a release of peptidyl-tRNA from the ribosomes. In the poly(A,C) model system, these antibiotics produced a 50% inhibition of amino-acid incorporation into total peptides, a 70% release of ribosome-bound peptidyl-tRNA, and a 95% repression of the synthesis of long peptide chains. The production of equivalent effects at saturating concentrations of these antibiotics in the four model systems examined is suggestive of a similarity in their mode of action. Our results indicate that 14-membered macrolides and type B synergimycins can act on ribosomes during the whole elongation process. The functional block produced by both antibiotics is usually reversible, but may result in a premature release of peptidyl-tRNA when the stability of ribosomal complexes is lowered by the incorporation of basic amino acids.

Anti-Bacterial Agents↗