Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Poly T”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1983

The effect of in vivo treatment with triiodothyronine on the in vitro synthesis of protein-poly(ADP)-ribose adducts by isolated cardiocyte nuclei and the separation of poly(ADP)-ribosylated proteins by phenol extraction and electrophoresis.

In vivo treatment of rats with triiodothyronine (30 micrograms/100 g of body weight for 4 consecutive days) inhibited poly(ADP)-ribose polymerase activity of cardiocyte nuclei, but low enzymatic activity of nuclei of noncardiocyte origin remained unaffected. RNA synthesis in cardiocyte nuclei isolated from triiodothyronine-treated rats was augmented. A positive correlation was observed between the degree of inhibition of poly(ADP)-ribose polymerase and cardiac ventricular enlargement in triiodothyronine-treated animals. RNA synthesis in isolated cardiocyte nuclei was inhibited by in vitro poly(ADP)-ribosylation only when cardiocyte nuclei were obtained from triiodothyronine-treated animals. In vitro poly(ADP)-ribosylated proteins were isolated from cardiocyte nuclei by solvent partitioning between phenol and aqueous phases. About 90% of the protein-poly(ADP)-ribose adducts partitioned into the aqueous fraction, and the chain length of polymers in this phase was between medium (n = 4-9) and long (n greater than 32), whereas the phenol phase contained protein-oligomer and monomer adducts. Not only the chain length of oligomers but the nature of modified proteins appeared to participate in determining the partitioning of polymer-protein adducts, and different proteins were separated from the two phases by gel electrophoresis. More than 90% of protein-polymer adducts formed by cardiocyte nuclei were not extracted by 0.25 N HCl, indicating prevalence of nonhistone proteins as polymer acceptors. Gel electrophoresis and near quantitative recovery of adducts in a gel system that protected from degradation of adducts to free polymers confirmed the predominance of nonhistone proteins as main acceptors and demonstrated an artifact of autoradiography that seemed to indicate histone H1 as a significant acceptor. Treatment with triiodothyronine diminished poly(ADP)-ribosylation of certain groups of proteins more than others, implying some degree of selectivity of action of the hormone. Catabolism of the polymer in vitro was not affected by triiodothyronine treatment.

Animals↗
PubMed1987

Interleukin 1 and poly(rI).poly(rC) induce production of a hybridoma growth factor by human fibroblasts.

Cultures of normal diploid fibroblasts and of a human osteosarcoma cell line (MG-63) are shown to be able to produce a factor which promotes the growth of B cell hybridomas (hybridoma growth factor, HGF). The induction is stimulated by treatment of the cells with interleukin 1 (IL 1) (alpha or beta) or polyriboinosinic-polyribocytidylic acid [poly(rI).poly(rC)]. Combined treatment with cycloheximide and actinomycin D also stimulates production and enhances production induced by IL 1 or poly(rI).poly(rC). Extremely small doses of IL 1 (0.1 units/ml) are active as inducer of HGF. Also, under optimal conditions the yield of HGF can attain as much as 10(4) units/ml. Tumor necrosis factor (TNF-alpha), which otherwise shares various properties with IL 1, is a weak inducer of HGF. Although there is a superficial resemblance between induction of HGF and that of interferon-beta, the two activities are serologically distinct and conditions for their induction are quite different. In fact, conditions for induction of HGF are indistinguishable from those described for the induction of the mRNA of the so-called 26-kDa protein (also known as interferon-beta 2). Finally, the HGF derived from IL 1- or poly(rI).poly(rC)-treated fibroblasts is serologically not distinguishable from that produced by mitogen-stimulated peripheral blood leukocytes.

Animals↗
PubMed1997

X-ray fibre diffraction study of an elevated temperature structure of poly(dA).poly(dT).

A reversible conformational transition between two discrete double helical forms of poly(dA).poly(dT) has been put into evidence by X-ray fibre diffraction. We observed that the transition between the well known B' conformation and a new helical structure (B*) occurs at a relative humidity near 80%, when the temperature is raised above 30 degrees C. It appears that the B* conformation is not just a distorted B' form of poly(dA).poly(dT) but rather a stable (up to a least 70 degrees C) distinct double helical structure of that polynucleotide. Analysis of X-ray patterns allowed us to present the geometrical parameters of a molecular model of this new double helix. It consists of 11.4 nucleotide pairs per turn in a pitch length of about 36.7 A. The proposed high-temperature right handed helical structure of poly(dA).poly(dT) is a member of the B-DNA family since the duplex has C1'-exo furanoses in both antiparallel but geometrically identical sugar-phosphate strands. The present finding may shed light on interpretations of results obtained from premelting or nucleosome formation processes involving (dA.dT) tracts in synthetic or natural DNA polymers.

Base Composition↗
PubMed1987

Abrogation of the tumor promoting effect of allogeneic blood transfusion by polyadenylic-polyuridylic acid (poly A-poly U).

Studies from several centers have shown an immunosuppressive effect of surgical procedures, whilst others have shown blood transfusion in association with cancer surgery to have an adverse effect on ultimate prognosis. We have previously demonstrated enhanced growth of tumor metastases, in rats following allogeneic blood transfusion and surgery. Polyadenylic-polyuridylic acid (poly A-poly U) has been reported to stimulate immune responses. In this report, we have investigated the effectiveness of poly A-poly U as an adjuvant to blood transfusion and surgical procedures in BN rats bearing artificial lung metastases. Significantly reduced tumor growth was observed, following poly A-poly U adjuvant treatment. These results lead to serious contemplation of the use of this drug as adjuvant therapy in blood transfused and surgically treated patients.

Adjuvants, Immunologic↗
PubMed1989

Depletion of hypothalamic norepinephrine reduces the fever induced by polyriboinosinic acid: polyribocytidylic acid (Poly I:Poly C) in rats.

Administration of either Poly I:Poly C (0.05-0.50 micrograms) or norepinephrine (2-8 micrograms) into the anterior hypothalamic area produced a dose-related fever in rats. The fever induced by Poly I:Poly C was attenuated after selective depletion of norepinephrine in the hypothalamus. However, selective depletion of hypothalamic norepinephrine did not affect the fever induced by intrahypothalamic norepinephrine. The data indicate that Poly I:Poly C may act to induce fever through the endogenous release of norepinephrine from the rat's hypothalamus.

Animals↗
PubMed2001

A new D-DNA form of poly(dA-dT).poly(dA-dT): an A-DNA type structure with reversed Hoogsteen pairing.

The D-DNA double helix model of poly(dA-dT).poly(dA-dT) proposed in the literature is not in accordance with some notable experimental facts and physicochemical conditions to which it is related. Thus, the fibre X-ray diffraction pattern of D-DNA obtained at a relative humidity lower than that giving the A-DNA form is singularly not taken into account when one assumes that there is only one D structure of B-DNA type. We rather suggest that there are actually two different forms of D-DNA, namely D(A) which partakes in the D-A-B transitions and D(B) associated with the D-B change of conformation. Although these two DNA structures have the same helical parameters (pitch and number of residues per turn), in agreement with X-ray data, their detailed conformations are considerably different. Whereas D(B) is indeed the structure generally defined as D-DNA, a critical analysis based on a comparison between different possible DNA double helices leads us to propose dihedral angles, a set of atomic coordinates and a stereo view of another new form of D-DNA, the D(A) structural model. It is a right-handed double helix with a dinucleotide as the repeat unit. The furanose rings are of the A-DNA type (C3' endo) and the bases are hydrogen bonded according to the reversed Hoogsteen pairing. Such a disposition renders the D(A) model unsuitable for poly(dI-dC).poly(dI-dC), the other alternating polynucleotide observed in the D(B) structure. The consistency of these two different D-DNA structures of poly(dA-dT).poly(dA-dT) with the general aspects of hydration and helix-helix transitions of DNA, as well as with the conformational variability of AT base sequences, is discussed.

Base Composition↗
PubMed1986

Interferon: a mediator of indoleamine 2,3-dioxygenase induction by lipopolysaccharide, poly(I) X poly(C), and pokeweed mitogen in mouse lung.

When C3H/He mice were treated with lipopolysaccharide, poly(I) X poly(C), or pokeweed mitogen, the serum interferon titer increased almost instantaneously (100-2000 units/ml), and then the pulmonary indoleamine 2,3-dioxygenase was induced 50- to 140-fold. The peaks corresponding to interferon induction always preceded (approximately 24 h) those corresponding to dioxygenase induction. In C3H/HeJ (lipopolysaccharide-nonresponder) mice, however, lipopolysaccharide was totally inert in induction of both interferon and dioxygenase, although treatment with poly(I) X poly(C) and pokeweed mitogen led to a remarkable increase in the serum interferon titer and the enzyme activity. When lymphocytes of C3H/HeJ mice were inactivated by X irradiation and then reconstituted by the transfer of spleen cells from C3H/He mice, both enzyme and interferon from C3H/HeJ mice thus treated were induced almost normally after the lipopolysaccharide treatment. In addition, murine interferon alpha/beta, which was injected intravenously in C3H/He or C3H/HeJ mice, almost instantaneously and dose-dependently induced the pulmonary enzyme, and at a dose of 10(5) units per mouse the enzyme activity was enhanced 20- to 26-fold in these two strains of mice. These results suggest that interferon, which is generated by the interaction of lymphocytes with lipopolysaccharide, poly(I) X poly(C), or pokeweed mitogen, is a mediator of indoleamine 2,3-dioxygenase induction in the mouse lung by these agents.

Animals↗
PubMed1984

Thermal melting of poly(dA-dT).poly(dA-dT) in methanol-water solutions.

Thermal melting of a synthetic DNA poly(dA-dT).poly(dA-dT) was investigated in methanol-water solutions. Methanol decreased melting temperature of the polynucleotide but the decrease was qualitatively different in the presence of milimolar concentrations of sodium and cesium cations. The difference is a consequence of the fact that poly(dA-dT).poly(dA-dT) undergoes a helix-helix conformational isomerization in methanol-water solutions which is cesium cation specific. The arising conformation is much more stable than the conformation which poly(dA-dT).poly(dA-dT) adopts in solutions with sodium cations at high methanol concentrations. The (A+T) rich DNA of Bacillus cereus displays a similar behaviour.

Hot Temperature↗
PubMed1985

RNA-like conformational properties of a synthetic DNA poly(dA-dU).poly(dA-dU).

Differences in the circular dichroism of poly(dA-dT).poly(dA-dT) and poly(dA-dU).poly(dA-dU) and in its temperature induced changes are reported. A comparison to the data obtained with DNA and RNA indicates that an absence of thymine methyl groups in the polynucleotide results in promoting its RNA-like conformational properties. However, poly(dA-dU).poly(dA-dU) is not an A-DNA type of double helix.

Animals↗
PubMed1976

An adjuvant effect of poly A - poly U on production of antibodies to DNA in rabbits.

The effect of polyadenylate-polyuridylate copolymer (poly A-poly U) on the formation of anti-DNA antibodies in rabbits was investigated. 1) Poly A-poly U proved to be an effective adjuvant for production of antibodies to DNA. These were elicited in rabbits at high titer and were formed at an early stage of immunizations. 2) The antiserum obtained reached potently with denatured DNA, but with neither methylated bovine serum albumin (MBSA) used as carrier protein nor poly A-poly U used as adjuvant. This was demonstrable both by C-fixation and double diffusion tests. 3) The antibodies occurred exclusively in the IgG fraction separated by Sephadex G-200 column chromatography.

Adjuvants, Immunologic↗
PubMed1977

The distribution of poly(A)+ and poly(A)- protamine messenger RNA sequences in the developing trout testis.

Protamine messenger RNA was isolated in a very pure form from trout testes and used as a template for the synthesis of labeled complementary DNA (cDNA) of high specifiv activity. The cDNA was found to be a full-length transcript of protamine messenger RNA and was used as a probe for hybridization reactions with RNA preparations isolated from three subcellular compartments of differentiating trout testis cells. The RNA populations from the nuclei, polysomes, and postribosomal supernatant of these cells were fractionated into poly(A)-containing [poly(A)+] and poly(A)-free [poly(A)-] RNA to determine the distribution of these two forms of protamine mRNA in these cell compartments. At the early protamine stage of testis development, polysomal and postribosomal supernatant fractions contain almost equal quantities of poly(A)+ protamine mRNA, but poly(A)- protamine mRNA was found almost entirely in the polysomes.

Animals↗
PubMed1981

Immune response modifying activity in mice of polyinosinic: polycytidylic acid stabilized with poly-L-lysine, in carboxymethylcellulose [poly-ICLC].

Poly-ICLC, a polyinosinic: polycytidylic acid stabilized with poly-L-lysine in carboxymethyl-cellulose was tested in mice for its immunoregulatory activity. Poly-ICLC was found to enhance T cell responsiveness but not B cells. It augmented the delayed type hypersensitivity response significantly. The results indicate Poly-ICLC to be a T cell stimulator. Macrophage tumoricidal activity was markedly enhanced both in vitro and in vivo after exposure to Poly-ICLC. Natural killer cell cytotoxicity was significantly augmented in vivo. Both macrophage and natural killer cell activity was maintained for over 3 days after only one treatment. The extended period of tumor cell cytotoxicity, exhibited by macrophages and natural killer cells, may correlate to Poly-ICLC induction of early and high levels of interferon which are maintained in the serum for a longer period of time.

Animals↗
PubMed2005

An essential cytoplasmic function for the nuclear poly(A) binding protein, PABP2, in poly(A) tail length control and early development in Drosophila.

Translational control of maternal mRNA through regulation of poly(A) tail length is crucial during early development. The nuclear poly(A) binding protein, PABP2, was identified biochemically from its role in nuclear polyadenylation. Here, we analyze the in vivo function of PABP2 in Drosophila. PABP2 is required in vivo for polyadenylation, and Pabp2 function, including poly(A) polymerase stimulation, is essential for viability. We also demonstrate an unanticipated cytoplasmic function for PABP2 during early development. In contrast to its role in nuclear polyadenylation, cytoplasmic PABP2 acts to shorten the poly(A) tails of specific mRNAs. PABP2, together with the deadenylase CCR4, regulates the poly(A) tails of oskar and cyclin B mRNAs, both of which are also controlled by cytoplasmic polyadenylation. Both Cyclin B protein levels and embryonic development depend upon this regulation. These results identify a regulator of maternal mRNA poly(A) tail length and highlight the importance of this mode of translational control.

Amino Acid Sequence↗
PubMedDate not supplied

Antitumoral action of interferon and poly(A)poly(U) on HeLa xenografts in the nude mouse.

The mechanism of the antitumoral action of interferon was investigated in athymic Nude mice grafted with HeLa tumour cells. Treatment of such mice with either mouse interferon, human interferon, a mixture of human and mouse interferon or an inducer of interferon, poly(A)poly(U), resulted in inhibition of tumour growth. The most significant inhibition was observed in mice treated with the mixture of the interferons or with poly(A)poly(U). The antitumoral action of interferon is probably mediated by two mechanisms, one which acts directly on tumour cells and another which acts indirectly by activation of one or several systems of the host. In the present study, the level of 2-5A synthetase in the tumour and the natural killer (NK) activity of splenic cells were used as markers to assess the direct and indirect actions of interferon, respectively. We provide evidence to suggest that both mechanisms are active in the antitumoral action of interferon. Enhanced levels of pppA(2'p5'A)n synthetase (2-5A synthetase) in the tumour after treatment with human interferon or poly(A)poly(U) provides biochemical evidence that interferon interacts with tumour cells in an organism (direct action of interferon). Enhanced levels of splenic NK cell activity as a result of injection or production of homologous interferon confirm the activation of the host's defense mechanisms (indirect action of interferon).

2',5'-Oligoadenylate Synthetase↗
PubMed1989

31P NMR spectra of ethidium, quinacrine, and daunomycin complexes with poly(adenylic acid).poly(uridylic acid) RNA duplex and calf thymus DNA.

31P NMR provides a convenient monitor of the phosphate ester backbone conformational changes upon binding of the intercalating drugs ethidium, quinacrine, and daunomycin to sonicated poly(A).poly(U) and calf thymus DNA. 31P chemical shifts can also be used to assess differences in the duplex unwinding angles in the presence of the drug. Thus a new 31P signal, 1.8-2.2 ppm downfield from the double-stranded helix signals, is observed in the ethidium ion-poly(A).poly(U) complex. This signal arises from phosphates which are in perturbed environments due to intercalation of the drug. This is in keeping with the hypothesis that the P-O ester torsional angle in phosphates linking the intercalated base pairs is more trans-like. Similar though smaller deshielding of the 31P signals is observed in sonicated poly(A).poly(U)-quinacrine complexes as well as in the daunomycin complexes. The effect of added ethidium ion, quinacrine, and daunomycin on the 31P spectra of sonicated calf thymus DNA is consistent with Wilson and Jones' (1982) earlier study. In these drug-DNA complexes the drug produces a gradual downfield shift in the DNA 31P signal without the appearance of a separate downfield peak. These differences are attributed to differences in the rate of chemical exchange of the drug between free and bound duplex states. The previous correlation of 31P chemical shift with drug duplex unwinding angle (Wilson & Jones, 1982) is confirmed for both the RNA and DNA duplexes.

DNA↗
PubMed2000

The phosphorylation state of poly(A)-binding protein specifies its binding to poly(A) RNA and its interaction with eukaryotic initiation factor (eIF) 4F, eIFiso4F, and eIF4B.

The poly(A)-binding protein (PABP) interacts with the eukaryotic initiation factor (eIF) 4G (or eIFiso4G), the large subunit of eIF4F (or eIFiso4F) to promote translation initiation. In plants, PABP also interacts with eIF4B, a factor that assists eIF4F function. PABP is a phosphoprotein, although the function of its phosphorylation has not been previously investigated. In this study, we have purified the phosphorylated and hypophosphorylated isoforms of PABP from wheat to examine whether its phosphorylation state affects its binding to poly(A) RNA and its interaction with eIF4G, eIFiso4G, or eIF4B. Phosphorylated PABP exhibited cooperative binding to poly(A) RNA even under non-stoichiometric binding conditions, whereas multiple molecules of hypophosphorylated PABP bound to poly(A) RNA only after free poly(A) RNA was no longer available. Together, phosphorylated and hypophosphorylated PABP exhibited synergistic binding. eIF4B interacted with PABP in a phosphorylation state-specific manner; native eIF4B increased the RNA binding activity specifically of phosphorylated PABP and was greater than 14-fold more effective than was recombinant eIF4B, whereas eIF4F promoted the cooperative binding of hypophosphorylated PABP. These data suggest that the phosphorylation state of PABP specifies the type of binding to poly(A) RNA and its interaction with its partner proteins.

Binding Sites↗
PubMed1983

Poly(dA-dT).poly(dA-dT) in low salt appears to be a left-handed B-helix combined use of chemical theory, fiber diffraction and NMR spectroscopy.

Poly(dA-dT).poly(dA-dT) can adopt the B- and D- forms in the fibrous state. Theoretical energy calculations and fiber diffraction analyses suggest that there can be three structural models of poly(dA-dT).poly(dA-dT) in each of these two forms viz right and left-handed Watson Crick models and left-handed Hoogsteen--a total of six possible models. Fiber data for the polymer in the B- or the D-form or energy calculations cannot distinguish any one model from the other. However, a comparison of observed proton chemical shifts with the theoretically computed ones and the NOE studies on exchangeable and nonexchangeable protons suggest that poly(dA-dT).poly(dA-dT) in low salt solution exists predominantly in the left-handed B-conformation.

Base Composition↗
PubMed1985

Two binding modes of netropsin are involved in the complex formation with poly(dA-dT).poly(dA-dT) and other alternating DNA duplex polymers.

Using CD measurements we show that the interaction of netropsin to poly(dA-dT).poly(dA-dT) involves two binding modes at low ionic strength. The first and second binding modes are distinguished by a defined shift of the CD maximum and the presence of characteristic isodichroic points in the long wavelength range from 313 nm to 325 nm. The first binding mode is independent of ionic strength and is primarily determined by specific interaction to dA.dT base pairs. Employing a netropsin derivative and different salt conditions it is demonstrated that ionic contacts are essential for the second binding mode. Other alternating duplexes and natural DNA also exhibit more or less a second step in the interaction with netropsin observable at high ratio of ligand per nucleotide. The second binding mode is absent for poly(dA).poly(dT). The presence of a two-step binding mechanism is also demonstrated in the complex formation of poly(dA-dT).poly(dA-dT) with the distamycin analog consisting of pentamethylpyrrolecarboxamide. While the binding mode I of netropsin is identical with its localization in the minor groove, for binding mode II we consider two alternative interpretations.

Binding Sites↗