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 559 records · Page 31Linked to original sources
PubMed1990

Bh-DNA: variations of the poly[d(A)].poly[d(T)] structure within the framework of the fibre diffraction studies.

A refinement of the recent results for poly[d(A)].poly[d(T)] (Alexeev et al., J. Biomol. Struct. Dyn. 4,989 (1987)) involving additional parameters of the base-pair structure and of the sugar-phosphate backbone expands the conformational potential of this polynucleotide of the B type to include the possibility of bifurcated hydrogen bonds of the kind recently discovered in crystalline deoxyoligonucleotide with lone d(A)n.d(T)n stretch (Nelson et al., Nature 330, 221 (1987)). Still, analysis of the available data and energy calculations do not seem to indicate that the bifurcated H-bonds are a crucial factor responsible for the anomalous structure of the d(A)n.d(T)n sequence. The unique structural properties of poly[d(A)].poly[d(T)] can hardly be explained without taking into account its interactions with the double-layer hydration spine in the minor groove. In view of the hydration mechanism stabilizing poly[d(A)].poly[d(T)] and of the polynucleotide's heteronomous prehistory (Arnott et al., Nucleic Acids Res. 11,4141 (1983)) we suggest that this B-type structure be called Bh.

Base Composition↗
PubMed1996

Reversal of the Z- to B-conformation of poly(dA-dT) center dot poly(dA-dT) induced by netropsin and distamycin A.

Poly(dA-dT) center dot poly(dA-dT) which adopts the Z-form at 5 M NaCl in presence of 95 mM Ni2+ions is reversed to the B-conformation by the nonintercalating drugs netropsin (Nt) and distamycin A (Dst). The drug-induced reversal from the Z-to B-form of poly(dA-dT) center dot poly(dA-dT) is evidenced by CD spectral changes at characteristic wavelengths around 295 nm and 248 nm. The drug-induced conformational transition is accompanied by a slow kinetic process. The results suggest the preference of these AT-specific drugs for the B-form and the inability of Nt and Dst to form a stable complex with the Z-form of poly(dA-dT) center dot poly(dA-dT).

Bacterial Proteins↗
PubMed2001

Antigenicity of poly(I) and ROS-poly(I) and their recognition of human anti-DNA autoantibodies.

The effect of hydroxyl radicals on polyinosinic acid [poly(I)] was studied. Strand breaks, base alteration and a decrease in absorbance at 248 nm (lambda max) were observed upon *OH modification of poly(I). The broad antigen specificity of the induced anti-poly(I) and anti-ROS-poly(I) antibodies showed diverse antigen binding characteristics similar to those of SLE autoantibodies. Recognition of both poly(I) and ROS-poly(I) by human SLE anti-DNA autoantibodies was observed. The possible significance of these findings in the etiology of SLE has been discussed.

Animals↗
PubMed1990

Interferon induction by viruses. XX. Acid-labile interferon accounts for the antiviral effect induced by poly(rI).poly(rC) in primary chick embryo cells.

Primary chick embryo cells which were "aged" in vitro and exposed to poly(rI).poly(rC) developed a disproportionately high degree of resistance to virus challenge in relation to the amount of conventional acid-stable interferon (IFN) produced. Cells were often highly resistant after exposure to a few nanograms of poly(rI).poly(rC) which gave rise to little or no acid-stable IFN. Study of the mechanism(s) responsible showed that this antiviral state was not due to the double-stranded ribonuclease induced in parallel, nor to residual poly(rI).poly(rC) (which this ribonuclease destroyed), but to the production of a hitherto undescribed acid-labile chicken IFN.

Acids↗
PubMed1991

Production of human interferon-beta by Sendai virus and poly(rI).poly(rC): inhibition by neomycin.

Neomycin inhibits the production of interferon-beta (IFN-beta) in human fibroblast cells in response to Sendai virus or to poly(rI).poly(rC) in a concentration-dependent manner, and to the greatest extent effective when added prior to or up to 2 h after induction. This inhibitory effect is negated when the protein kinase C activator, SC-9, is present during IFN-beta production in response to poly(rI).poly(rC), but not in response to Sendai virus. These results suggest that in human cells both virus and poly(rI).poly(rC) utilize an early neomycin-sensitive signal transduction step for the production of IFN-beta; because neomycin binds specific phosphatidylinositol phosphates, both of these inducers very likely require hydrolysis of these phosphates.

Cell Line↗
PubMed2003

Stimulation of poly(A) polymerase through a direct interaction with the nuclear poly(A) binding protein allosterically regulated by RNA.

During polyadenylation of mRNA precursors in metazoan cells, poly(A) polymerase is stimulated by the nuclear poly(A) binding protein PABPN1. We report that stimulation depends on binding of PABPN1 to the substrate RNA directly adjacent to poly(A) polymerase and results in an approximately 80-fold increase in the apparent affinity of poly(A) polymerase for RNA without significant effect on catalytic efficiency. PABPN1 associates directly with poly(A) polymerase either upon allosteric activation by oligo(A) or, in the absence of RNA, upon deletion of its N-terminal domain. The N-terminal domain of PABPN1 may function to inhibit undesirable interactions of the protein; the inhibition is relieved upon RNA binding. Tethering of poly(A) polymerase is mediated largely by the C-terminal domain of PABPN1 and is necessary but not sufficient for stimulation of the enzyme; an additional interaction dependent on a coiled-coil structure located within the N-terminal domain of PABPN1 is required for a productive interaction.

Allosteric Regulation↗
PubMed1975

The dependence of successful immunotherapy on adequate tumor burden as shown by the treatment of AKR leukemia with poly A-poly U.

The therapeutic efficacy of polyadenlyic-polyuridylic acid (poly A-poly U) on the transplantable AKR leukemia varied with the dose of tumor cells implanted. The greater the number of AKR tumor cells injected into 8-week-old AKR mice free of clinical evidence of cancer, the greater the effect of poly A-poly U in mediating host immunologic control of the tumor. Poly A-poly U was either ineffective or could enhance tumor growth when smaller doses of tumor cells were transferred. The efficacy of an immune adjuvant depended on a tumor burden affording optimum host responsiveness. This does not necessarily arise in the host bearing minimal tumor burden.

Adjuvants, Immunologic↗
PubMed1976

Recognition of polynucleotides by antibodies to poly(I), poly(C).

The binding of anti poly(I). poly (C) Fab fragments to double or triple stranded polynucletides has been studied by fluorescence. Association constants were deduced from competition experiments. The comparison of the association constants leads to the conclusion that several atoms of the base residues do not interact with the amino acid residues of the binding site of Fab fragment while the hydroxyl groups of furanose rings interact. These results suggest that the Fab fragments do not bind to the major groove of the double stranded polynucleotides. An interaction between the C(2)O group of pyrimidine residues and Fab fragments cannot be excluded. Circular dichroism of poly(I). poly(C) or poly(I). poly(br5C)-Fab fragments complexes are very different from the circular dichroism of free polynucleotides which suggests a deformation of the polynucleotides bound to the Fab fragments.

Antigen-Antibody Complex↗
PubMed1978

Effect of DNA on poly (ADP-ribose) glycohydrolase and the degradation of histone H1-poly (ADP-ribose) complex from HeLa cell nuclei.

A poly(ADP-ribose)-H1 histone complex has been isolated from HeLa cell nuclei incubated with NAD. The rate of poly(ADP-ribose) glycohydrolase catalyzed hydrolysis of the polymer in the complex is only 1/9 that of free poly(ADP-ribose), indicating that the polymer is in a protected environment within the complex. Comparison of the rate of hydrolysis of free poly(ADP-ribose) in the presence or absence of H1 to that in the complex synthesized de novo indicates a specific mode of packaging of the complex. This is further indicated by the fact that alkaline dissociation of the complex followed by neutralization markedly exposes the associated poly(ADP-ribose) to the glycohydrolase. The complex also partially unfolds when it binds to DNA as evidenced by a 2-fold increase in the rate of glycolytic cleavage of poly(ADP-ribose). This effect of DNA is not due to a stimulation of the glycohydrolase per se since hydrolysis of free polymer by the enzyme is strongly inhibited by DNA, especially single-stranded DNA. Inhibition of glycohydrolase by DNA results from the binding of the enzyme to DNA and conditions which decrease this binding (increased ionic strength or addition of histone H1 which competes for DNA binding) relieve the DNA inhibition.

Cell Nucleus↗
PubMed1981

Nucleosomes will not form on double-stranded RNa or over poly(dA).poly(dT) tracts in recombinant DNA.

We have been unable to "force" double-stranded RNA to fold into nucleosome-like structures using several different histone-RNA "reconstitution" procedures. Even if the histones are first stabilized in octameric form by dimethylsuberimidate cross-linking they are still unable to form specific complexes with the RNA. Moreover double-stranded RNA is unable to induce histones to assemble into octamers although we confirm that the non-nucleic acid homopolymer, polyglutamic acid, has this ability. We have also determined, using pyrimidine tract analysis, that nucleosomes will not form over a sufficiently long segment of poly(dA).poly(dT) in a recombinant DNA molecule. Thus nucleosomes cannot fold DNA containing an 80 base pair poly(dA).poly(dT) segment but a 20 base pair segment can be accommodated in nucleosomes fairly well. Segments of intermediate length can be accommodated but are clearly selected against. Poly(dA).poly(dT) differs only slightly from natural DNA in helix structure. Therefore either this homopolymer resists folding, or nucleosomes are very exacting in the nucleic acid steroid parameters they will tolerate. Such constraints may be relevant to nucleosome positioning in chromatin.

Animals↗
PubMed1990

Partial release of AcPhe-Phe-tRNA from ribosomes during poly(U)-dependent poly(Phe) synthesis and the effects of chloramphenicol.

Poly(U)-programmed 70S ribosomes can be shown to be 80% to 100% active in binding the peptidyl-tRNA analogue AcPhe-tRNA to their A or P sites, respectively. Despite this fact, only a fraction of such ribosomes primed with AcPhe-tRNA participate in poly(U)-directed poly(Phe) synthesis (up to 65%) at 14 mM Mg2+ and 160 mM NH4+. Here it is demonstrated that the apparently 'inactive' ribosomes (greater than or equal to 35%) are able to participate in peptide-bond formation, but lose their nascent peptidyl-tRNA at the stage of Ac(Phe)n-tRNA, with n greater than or equal to 2. The relative loss of early peptidyl-tRNAs is largely independent of the degree of initial saturation with AcPhe-tRNA and is observed in a poly(A) system as well. This observation resolves a current controversy concerning the active fraction of ribosomes. The loss of Ac(Phe)n-tRNA is reduced but still significant if more physiological conditions for Ac(Phe)n synthesis are applied (3 mM Mg2+, 150 mM NH4+, 2 mM spermidine, 0.05 mM spermine). Chloramphenicol (0.1 mM) blocks the puromycin reaction with AcPhe-tRNA as expected but, surprisingly, does not affect the puromycin reaction with Ac(Phe)2-tRNA nor peptide bond formation between AcPhe-tRNA and Phe-tRNA. The drug facilitates the release of Ac(Phe)2-4-tRNA from ribosomes at 14 mM Mg2+ while it hardly affects the overall synthesis of poly(Phe) or poly(Lys).

Binding Sites↗
PubMed2005

Chromatin architecture and functions: the role(s) of poly(ADP-RIBOSE) polymerase and poly(ADPribosyl)ation of nuclear proteins.

Epigenetic states that allow chromatin fidelity inheritance can be mediated by several factors. One of them, histone variants and their modifications (including acetylation, methylation, phosphorylation, poly(ADP-ribosyl)ation, and ubiquitylation) create distinct patterns of signals read by other proteins, and are strictly related to chromatin remodelling, which is necessary for the specific expression of a gene, and for DNA repair, recombination, and replication. In the framework of chromatin-controlling factors, the poly(ADP-ribosyl)ation of nuclear proteins, catalysed by poly(ADP-ribose)polymerases (PARPs), has been implicated in the regulation of both physiological and pathological events (gene expression/amplification, cellular division/differentiation, DNA replication, malignant transformation, and apoptotic cell death). The involvement of PARPs in this scenario has raised doubts about the epigenetic value of poly(ADP-ribosyl)ation, because it is generally activated after DNA damage. However, one emerging view suggests that both the product of this reaction, poly(ADP-ribose), and PARPs, particularly PARP 1, play a fundamental role in recruiting protein targets to specific sites and (or) in interacting physically with structural and regulatory factors, through highly reproducible and inheritable mechanisms, often independent of DNA breaks. The interplay of PARPs with protein factors, and the combinatorial effect of poly(ADPribosyl)ation with other post-translational modifications has shed new light on the potential and versatility of this dynamic reaction.

Adenosine Diphosphate Ribose↗
PubMed1986

Glucocorticoid-induced cell death and poly[adenosine diphosphate(ADP)-ribosyl]ation: increased toxicity of dexamethasone on mouse S49.1 lymphoma cells with the poly(ADP-ribosyl)ation inhibitor benzamide.

Treatment of S49.1 mouse lymphoma cells with the synthetic glucocorticoid dexamethasone resulted in a delayed cell death. During the 24-h latency period, DNA, RNA, and protein synthesis fell to about 50%, 60%, and 30% of control values, respectively, without a change in ATP levels, the latter suggesting cellular integrity. The onset of cellular suicide was characterized by the occurrence of DNA strand breaks, finally leading to the total digestion of internucleosomal DNA. Concomitant with the appearance of DNA fragmentation, poly(ADP-ribosyl)ation was activated, a process probably involved in DNA repair. Activation of poly(ADP-ribose)synthetase was paralleled by a fall in the level of the substrate NAD. An antagonistic role of poly(ADP-ribosyl)ation in glucocorticoid-induced cell death was suggested by the observation that low concentrations of the potent poly(ADP-ribose)synthetase inhibitor benzamide enhanced the toxicity of dexamethasone several-fold and shortened the interval between steroid addition and the onset of cell death. In addition, the fall in NAD was prevented by benzamide. The antagonistic function of poly(ADP-ribosyl)ation in glucocorticoid-induced cell death is, therefore, comparable to the role of the poly(ADP-ribose)synthetase in cells treated with alkylating agents, suggesting involvement of a DNA repair phenomenon in opposition to the mechanism of glucocorticoid-induced cell death.

Adenosine Triphosphate↗
PubMed1985

Pharmacokinetic and therapeutic activity of polyinosinic-polycytidylic acid stabilized with poly-L-lysine in carboxymethylcellulose [poly(I,C)-LC].

Polyinosinic-polycytidylic acid stabilized with poly-L-lysine in carboxymethylcellulose [poly(I,C)-LC] significantly augmented natural killer (NK) cell activity in several tissues. Macrophage (M phi) tumoricidal activity was also markedly increased. Both effector cells were active for 9 days. Poly(I,C)-LC also increased effector cell response in vitro. Injections of poly(I,C)-LC resulted in elevated effector cell responses in four of five routes tested. Treatment with poly(I,C)-LC led to an earlier reconstitution of bone marrow cells, NK cell activity, and M phi effector cell activity in mice pretreated with cyclophosphamide (Cytoxan). Combined treatment of MBL-2 tumor cells with cytoreductive chemotherapy and poly(I,C)-LC resulted in an enhanced therapeutic response.

Animals↗
PubMed1983

Effect of interferon on thoracic duct lymphocyte output: induction with either poly I:poly C or vaccinia virus.

Systemic inoculation of the interferon (IFN) inducer polyinosinic-polycytidylic polyribonucleotide (poly I:poly C) into CBA/J mice produces a significant decrease in the number of thoracic duct lymphocytes (TDL) collected 6 to 22 hr after injection. The number of TDL is restored to normal levels by 48 to 64 hr. Residual TDL collected during the inhibition period of poly I:poly C treatment showed a phenotypic profile similar to phosphate-buffered saline- (PBS) treated control groups when examined for Lyt-1.1, Lyt-2, Thy-1.2 and Iak surface markers. Interferon is implicated as the mediator of this phenomenon since: 1) Inoculation of exogenous IFN can induce a similar suppression in the number of recoverable TDL. 2) Pretreatment of mice with sheep anti-murine IFN serum can block this effect of poly I:poly C. Similar experiments with vaccinia virus demonstrate that although live virus can partially suppress the TDL output, almost complete suppression is achieved with ultraviolet (UV)-inactivated virus. Vaccinia virus-induced suppression of the number of TDL also appears to be caused by IFN since: 1) UV-inactivated virus induces significantly higher serum levels of IFN in comparison to live virus. 2) The suppression of TDL output by either live or UV-inactivated vaccinia virus can be blocked by pretreatment with anti-murine IFN. These findings suggest that the immunosuppression often associated with viral infections may be at least partially due to a decrease in lymphocyte recirculation mediated by the IFN initially released in response to the virus.

Animals↗
PubMed1978

Phase I-II trials of poly IC stabilized with poly-L-lysine.

Poly IC, stabilized with poly-L-lysine and carboxymethyl cellulose (poly ICLC), resists hydrolysis by primate serum (unlike the parent compound), induces high levels of serum interferon, and is effective in acute viral infections of subhuman primates. In a phase I-II clinical trial, poly ICLC was given iv in 15 daily doses of 0.5-27.0 mg/m2 to 19 patients with various solid tumors and to six patients with acute leukemia (1-65 years of age). At least three complete trials were conducted at each of six dose levels. Toxic reactions included fever (in 100% of trials), nausea (44%) hypotension (28%), thrombocytopenia and leukopenia (68%), erythema (12%), and polyarthralgia plus myalgia (16%). Hypotension and arthralgia-myalgia were related to dose level and/or magnitude of interferon induction, but other toxic manifestations were not. Poly ICLC induced significant serum interferon levels in 76% of trials, and the correlation between dose and peak interferon titer was linear. The maximum tolerated dose for all patients at a given drug dose was 12 mg/m2; at this dose, the mean peak interferon titer was 1940 reference units/ml. At a dose of 18 mg/m2, the mean peak interferon titer was 4473 reference units/ml, but severe myalgia and arthralgia were intolerable in at least half of the patients, and most had significant hypotension. At a dose of 27 mg/m2, one patient had acute renal failure. At high doses, iv poly ICLC also induced interferon in the cerebrospinal fluid.

Adolescent↗
PubMed1993

Stimulation of poly(A) tail elongation by the VP39 subunit of the vaccinia virus-encoded poly(A) polymerase.

The VP55 subunit of the vaccinia virus-encoded poly(A) polymerase can add a maximum of 35 adenylates to the 3'-end of an RNA primer in a rapid and highly processive manner, whereas the VP55-VP39 heterodimer catalyzes the formation of poly(A) tails several hundred nucleotides in length. Here, we describe the overexpression of the VP39 subunit, its purification to near homogeneity, and its ability to associate physically with VP55 and to stimulate polyadenylation. Although VP39 possessed no independent poly(A) polymerase activity, RNA primers with oligo(A) tails greater than 30 adenylates in length could be extended nearly 40-fold more rapidly in the presence of VP39. VP39 enhanced the polyadenylation rate by converting the slow, nonprocessive polyadenylation occurring after the rapid burst in the presence of monomeric VP55, to a rapid, semiprocessive reaction. The effect of VP39 was dramatic when poly(A) primers were used as, 60 mM NaCl, VP39 enhanced the polyadenylation rate 500-fold, and at 90 mM NaCl VP39 was absolutely required. Nevertheless, the VP39-containing polymerase remained selective for polyadenylation of an mRNA 3'-end in the presence of excess poly(A). These data suggest that the role of VP39 in polyadenylation is to increase the affinity of the polymerase for the growing poly(A) tail.

Bacteriophage T7↗
PubMed1976

[Antiviral activity of a poly A-poly U complex administered by various routes].

Interferon-inducing and antiviral activity of a synthetic polyribonucleotide, polyaenylic and polyuridylic acid complex (poly A--poly U) was studied comparatively on a model of experimental infection of albino mice caused by Venezuela Horse Encephalomyeliti Viruos (VHEV) using oral and intraperitoneal administration of the complex. It was shown that dm-interferon induction and antiviral effect comparatively high doses of poly A--poly U (Reanal) were required (1 mg/mouse). The highest antiviral effect was observed after a two-fold administration of the drug (24 hours and immediately before infection). It was more evident after intraperitoneal administration of the inductor. The interferon titers in the animal blood serum after intraperitoneal or oral administration of poly A--poly U were almost the same 58=60+/- +/- 18.9 IU50/ml).

Administration, Oral↗