Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RNA Aggregation”

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 37 records · Page 2Linked to original sources
PubMed1975

RNA polymerase stimulation: effect of aldosterone and other adrenocorticoids on RNA turnover in rat kidney.

The results of steroid hormone stimulation of aggregate RNA polymerase ?activity in kidney can be interpreted in terms of either template or enzyme alterations. In order to discover the effect of aldosterone on enzyme or DNA template, the RNA polymerases were purified from kidney nuclei of normal, adrenalectomized or adrenalectomized plus aldosterone treated rats and the activity was determined using different sources of DNA. It was found that the DNA from aldosterone treated rats was transcribed more efficiently than from other sources. Aldosterone does not seem to have a direct effect on the RNA polymerase. Fractionation of ([14-C]aldosterone injected) kidney chromatin revealed the presence of radioactivity in the non-histone acidic proteins and DNA, suggesting the possible binding of aldosterone or aldosterone-receptor complex to these chromatin fractions which may result in enhanced template activity. Turnover of RNA was also studied in various subcellular fractions: nuclei, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, polysomes, ribosomes and sRNA, in normal, adrenalectomized, and adrenalectomized plus adrenocortical hormone treated rat kidney, by following the loss of radioactivity after a single injection of [14-C]-orotic acid. Daily administration of aldosterone or deoxycorticosterone reversed the effects of adrenalectomy. Daily administration of corticosterone was without effect.

Adrenal Glands↗
PubMed1978

Induced cell aggregation and mating in Streptococcus faecalis: evidence for a bacterial sex pheromone.

Recipient strains of Streptococcus faecalis produce a trypsin sensitive, heat resistant, nuclease resistant factor, designated clumping-inducing agent (CIA) which causes strains carrying certain conjugative plasmids to aggregate. RNA and protein synthesis but not DNA synthesis are required for aggregation to occur. Recipient filtrates that contain CIA activity also induce donors to mate at high frequencies. Introduction of a transferable plasmid into strains producing CIA dramatically reduces the amount of CIA activity produced by the strain but allows the strain to respond to exogenously added CIA. Our data suggest that CIA represents a bacterial sex hormone (pheromone).

Animals↗
PubMed1985

Autoradiographic analysis of RNA synthesis in the oocyte-nurse cell complex of the polychaete Ophryotrocha labronica.

Females of the polychaete Ophryotrocha labronica have been pulse labelled with [5-3H] uridine, and the incorporation of label into the RNA of the oocyte-nurse cell complex was followed by light and electron microscope autoradiography. Up to its regression the polyploid nurse cell displays an intense synthesis of rRNA and mRNA, which sustains an extensive production of electron-dense protein granules in it. Concomitantly rRNA and mRNA are synthesized also in the oocyte. Short-term treatment (7h) of polychaete females with alpha-amanitin provokes serious disturbances of oogenesis and subsequent embryonic development, irrespective of when it is applied during oogenesis. In contrast actinomycin gives such effects only when it is applied at the onset of oogenesis. A previous investigation has demonstrated that nurse cell granules are gradually exported through an intercellular canal to the oocyte, where a fraction of them is incorporated into the typical yolk granules. The present labelling experiments indicate that nurse cell RNA is associated with the exported yolk precursor material. From inhibition experiments with alpha-amanitin and from in situ hybridizations with a poly(U)probe it appears that mRNA is particularly involved. At the final collapse of the nurse cell practically all its contents are transferred to the oocyte. From that time the ooplasm is found to contain nuage-like RNA aggregates, which in contrast to other [5-3H]uridine-labelled ooplasmic structures (yolk granules, and minor granules and aggregates) have a non-uniform distribution. The possible origin and function of these aggregates is discussed. The investigation indicates that the nurse cell has a significant export of RNA essentially similar to that from insect nurse cells.

Amanitins↗
PubMed1973

Analysis of high-molecular-weight ribonucleic acid associated with intracisternal A particles.

Intracisternal A particles, known primarily for their association with various tumors, have been shown to contain high-molecular-weight (HMW) ribonucleic acid (RNA) by velocity centrifugation, using linear glycerol gradients. This HMW RNA is sensitive to ribonuclease digestion and alkali treatment but is resistant to Pronase treatment. By a double-labeling experiment, HMW RNA was shown to be intrinsic to intracisternal A particles and not to have resulted from cytoplasmic polysomal RNA aggregation. By a reconstitution experiment, it was determined that the results were not due to C-type virus contamination. The synthesis of HMW RNA in intracisternal A particles is inhibited by actinomycin D and ethidium bromide. These observations emphasize that there are probably some taxonomic relationships between intracisternal A particles and oncogenic RNA viruses.

Animals↗
PubMed1968

Replication of bacteriophage ribonucleic acid: analysis of the ultrastructure of the replicative form and the replicative intermediate of bacteriophage R17.

A detailed qualitative and quantitative comparison was made of the ultrastructure of single-stranded ribonucleic acid (RNA) from bacteriophage R17 and double-stranded replicative form (RF) and replicative intermediate (RI) from cells infected with this bacteriophage. The nucleic acids were prepared for electron microscopy by the protein monolayer spreading technique of Kleinschmidt. Single-stranded RNA aggregated during spreading in the absence of urea, whereas RF and RI did not. On the other hand, RF and RI appeared to be susceptible to shear during spreading, whereas R17 RNA was not. From the maximal length of RF, a base translation of 3.14 A was calculated. This value favors a 10-fold helix model of double-stranded RNA. The same base translation was found for R17 RNA, indicating a stacked base structure for single-stranded RNA spread in the presence of urea. RI is a branched structure and the branches are removed by ribonuclease treatment. The branches are believed to be nascent single-stranded viral RNA. The contour length of the branch was equal to the contour length of the main chain up to the branch point, as predicted from theoretical analysis of the replication of viral RNA. The structure of RF and the main chain of RI was also analyzed by plotting the log (end-to-end distance squared) versus log (contour length). This demonstrated structures intermediate in stiffness between a random coil and a rigid rod.

Coliphages↗
PubMed1978

Basophil histamine release by RNA, DNA and aggregated IgG examined in rheumatoid arthritis and systemic lupus erythematosus. Results compared with basophil counts and antinuclear antibodies.

Basophils from patients with rheumatoid arthritis (RA) respond to RNA, DNA and immune complexes (aggregated IgG) with histamine release. The RNA response was well correlated to the clinical activity of the disease, since histamine liberation was found in all patients with severe activity, whereas no liberation was observed in patients with moderate or quiescent activity. A less significant correlation was obtained with DNA and aggregated IgG. In contrast, no response was obtained with RNA, DNA and aggregated IgG in patients with systemic lupus erythematosus (SLE) or in controls. In the RA and the SLE groups no significant correlation was found between the response of RNA, DNA and aggregated IgG and the serum titres of anti-DNA and antinuclear antibodies. No difference in basophil cell count in peripheral blood and basophil histamine content was found between RA, SLE and controls. Our results point to an involvement of an autoimmune type I reaction in the pathogenesis of RA directed against the nuclear components RNA and DNA and against immune complexes.

Adolescent↗
PubMed1991

VPg-mediated aggregation of potyviral RNA.

RNA prepared from the potyvirus tobacco vein mottling virus contained aggregates of the 9.5 kb genomic RNA with electrophoretic mobilities corresponding to 20 and 41 kb species. Similar aggregates were present in preparations of the RNAs of two other potyviruses. Aggregation occurred during or after purification of the RNA by sucrose gradient centrifugation and alcohol precipitation and was dependent upon the presence of a protein apparently bound covalently to a region at or near the 5' terminus of the viral RNA. This protein is probably the VPg. The RNAs of tobacco mosaic virus and cowpea mosaic virus did not form aggregates when isolated from purified virus by similar procedures.

Electrophoresis, Agar Gel↗
PubMed1976

Poly(A)-containing RNA in Tetrahymena pyriformis.

Poly(A)-containing RNAs with sedimentation coefficients in the range 10-45 S and 10-35 S (Mr 0.2-3.3 x 10(6) and 0.2-2.2 x 10(6) approximately) are present in the nucleus and cytoplasm of T. pyriformis respectively. The poly(A) segments present in both nuclear and cytoplasmic poly(A)-containing RNAs have a chain length of 80 - 150 nucleotides. Significant amounts of high-molecular-weight poly(A)-containing RNAs (35 S, Mr 2.2 x 10(6) are found in the post-polysomal fraction of the cytoplasm (messenger ribonucleoprotein particles?) and also in large polysomes. In order to exclude the possibility that these high-molecular-weight species are products of non-specific aggregation, RNA preparations were submitted to severe denaturing conditions before analysis and all electrophoreses were carried out in the presence of 95% (v/v) formamide.

Animals↗
PubMed1989

Bryostatin 1 induces differentiation of B-chronic lymphocytic leukemia cells.

Peripheral blood cells from nine patients with B-chronic lymphocytic leukemia (B-CLL) were treated in vitro with bryostatin 1 (a macrocyclic lactone derived from a marine invertebrate). Like the phorbol ester 12-0-tetradecanoyl-phorbol 13-acetate (TPA), bryostatin 1 activates protein kinase C (PKC), which plays a central role in the phosphatidylinositol signal transduction pathway. The effects of bryostatin 1 alone and in combination with TPA or with the calcium mobilizing ionophore A23187 were assessed by morphological appearance, cell adherence and aggregation, RNA and DNA synthesis, and immunoglobulin (Ig) production. While eight of nine B-CLL cultures remained proliferatively inert, bryostatin 1 could effectively trigger activation and differentiation of B-CLL cells in all cases as inferred by the induction of morphological changes, RNA synthesis, and monotypic Ig production. Addition of calcium ionophore A23187 to bryostatin 1-exposed cells resulted in significantly increased values for RNA synthesis and Ig production and in the acquisition of plasmacytoid morphology. Bryostatin 1 and the dual signal of bryostatin 1 plus A23187 mimicked the stimulatory action of TPA and the combination of TPA plus A23187, respectively. Overall, bryostatin 1 was less active than equivalent concentrations of TPA. This lesser efficacy may, however, reflect a quantitative rather than qualitative difference. Bryostatin 1 partially antagonized TPA-mediated effects on B-CLL cells suggesting different modes of action by the two activators. These studies indicate that bryostatin 1 has effective differentiation-inducing properties on B-CLL cells that can differentiation-inducing properties on B-CLL cells that can be accentuated by a calcium ionophore.

Aged↗
PubMed2000

Anti-hepatitic C virus antibodies hidden in circulating antibody/antigen aggregates in HCV-RNA positive patients.

The aim of this study was to determine whether antibodies to HCV can be hidden in immunocomplex aggregates in anti-hepatitis C virus (HCV) negative, HCV-RNA positive patients and whether their presence could be related to HCV viral load or HCV genotype. Sera (23 in toto) from patients with elevated alanine aminotransferase (ALT) levels and negative for anti-HCV but positive for HCV-RNA and the immunocomplex aggregates (precipitate with PEG 6000 and glycine 1 M) were studied. The sera were treated using a rapid, simple new ELISA which disrupted the immunocomplex aggregates. Sera from ten patients were tested anti-HCV positive after immunocomplex disruption. No correlation with age, sex, ALT level, viral load or HCV genotype was observed. In some patients anti-HCV antibodies were hidden in circulating antibody/antigen complexes which could be dissociated with a simple, inexpensive and rapid protocol; therefore it can provide a valuable addition to the diagnosis of HCV infection and it may prevent some cases of post-transfusion hepatitis.

Adult↗
PubMed2026

Nuclear export modulates TDP-43 phase transition and cytoplasmic aggregation.

RNA-binding protein TAR DNA-binding protein 43 (TDP-43) can form liquid-like, nuclear assemblies whose phase behavior may influence its aggregation propensity and neurotoxic activity. The mechanism(s) that modulates the transition of TDP-43 from a liquid to solid phase is poorly defined. Here we combine chemical and genome-wide genetic screenings to identify cellular factors that modulate the phase behavior of an RNA-binding defective TDP-43 mutant that mimics an Amyotrophic Lateral Sclerosis (ALS)-associated variant. Our screens uncover multiple cellular processes including RNA splicing, protein translation, proteostasis imbalance and nuclear export as TDP-43 phase regulators. Importantly, TDP-43 phase transition can be dynamically recapitulated in vitro in a semi-permeabilized cell system, which reveals that the inhibition of nuclear export reshapes the nuclear environment in favor of an RNA-dependent TDP-43 liquid-liquid phase separation (LLPS) state, which mitigates cytoplasmic TDP-43 aggregation. We validated this mechanism in a brain organoid model bearing an ALS-associated mutation, showing that nuclear export deficiency can limit pathogenic phospho-TDP-43 accumulation. These findings establish nuclear export as a key regulator of TDP-43 phase transitions and define a mechanistic framework that links altered nuclear transport and phase dynamics to TDP-43 aggregation potential.

Amyotrophic Lateral Sclerosis (ALS)↗
PubMed2026

Cellular modifiers of TDP-43 phase transition and cytoplasmic aggregation.

RNA-binding protein TAR DNA-binding protein 43 (TDP-43) can form liquid-like nuclear assemblies whose phase behavior is thought to influence its aggregation propensity and neurotoxic activity. The mechanisms that govern the liquid-to-solid phase transition of TDP-43 remain poorly defined. Here, we combined chemical and genome-wide genetic screens to identify cellular factors that modulate the phase behavior of an RNA-binding-defective TDP-43 mutant. Our screens uncovered multiple cellular processes, including RNA splicing, protein translation, proteostasis imbalance, and nuclear export as TDP-43 phase regulators. We also developed a semi-permeabilized cell system that partially recapitulates the TDP-43 phase transition in vitro, and showed that nuclear export inhibition reshapes the nuclear environment to favor RNA-dependent liquid-liquid phase separation (LLPS) of TDP-43, which mitigates its aggregation. Nuclear export inhibition in a brain organoid model bearing an ALS-associated mutation reduces pathogenic phospho-TDP-43 accumulation. These findings identify multiple modulators of TDP-43 phase transitions in a sensitized model system and establish a framework for further dissecting the link between nuclear transport and TDP-43 phase dynamics.

DNA-Binding Proteins↗
PubMed1998

Properties and growth mechanism of the ordered aggregation of a model RNA by the HIV-1 nucleocapsid protein: an electron microscopy investigation.

NCp7, the nucleocapsid protein of the human immunodeficiency virus type 1, induces an ordered aggregation of RNAs, a mechanism that is thought to be involved in the NCp7-induced promotion of nucleic acid annealing. To further investigate this aggregation the morphology and the properties of the NCp7-induced aggregates of the model RNA homoribopolymer, polyA, were investigated by electron microscopy in various conditions. In almost all the tested conditions, the aggregates were spherical and consisted of a central dense core surrounded by a less dense halo made of NCp7-covered polyA molecules. The formation of these aggregates with a narrow distribution of sizes constitutes a distinctive feature of NCp7 over other single-stranded nucleic acid binding proteins. In most conditions, at the shortest times that can be reached experimentally, all the polyA molecules were already incorporated in small aggregates, suggesting that the nucleation step and the first aggregation events took place rapidly. The aggregates then orderly grew with time by fusion of the smaller aggregates to give larger ones. The aggregate halo was important in the fusion process by initiating the bridging between the colliding aggregates. In the presence of an excess of protein, the aggregates grew rapidly but were loosely packed and dissociated easily, suggesting adverse protein-protein interactions in the aggregates obtained in these conditions. In the presence of an excess of nucleotides, the presence of both amorphous nonspherical and slowly growing spherical aggregates suggested some changes in the mechanism of aggregate growth due to an incomplete covering of polyA molecules by NCp7. Finally, we showed that in the absence of added salt, the aggregate fusions were unfavored but not the initial events giving the first aggregates, the reverse being true in the presence of high salt concentrations (> or = 300 mM).

Binding Sites↗
PubMed1991

Thermal stability of turnip yellow mosaic virus RNA: effect of pH and multivalent cations on RNA deaggregation and degradation.

Light scattering studies of RNA isolated from turnip yellow mosaic virus (TYMV) revealed a molar mass of 1.9.10(6) g mol-1, which is close to the value of 2.0.10(6) g mol-1 published for intact genomic TYMV RNA (2M RNA). However, gel electrophoresis under denaturing conditions demonstrated that only 30-40% of this native RNA was 2M RNA. Sucrose gradient centrifugation revealed the occurrence of a series of smaller RNA size classes, the mass ratios of which were greatly influenced by the pH of the solution and the presence of EDTA. These results suggest that native TYMV RNA preparations originally contain a mixture of intact RNA particles and of aggregates of RNA fragments with the same molar mass of about 2.10(6) g mol-1, and that the size classes are intermediates in the deaggregation process of the degraded genomic TYMV RNA. The native RNA displayed pH-dependent deaggregation and degradation. The degradation process of 2M RNA followed (pseudo) first-order kinetics. Lower degradation rates were observed for RNA depleted of divalent cations and polyamines. For depleted 2M RNA an enthalpy of activation of about 100 kJ mol-1 and an almost zero entropy of activation was calculated. Similar values were also found for depleted E. coli ribosomal RNAs and depleted MS2 RNA, demonstrating that all RNAs are equally vulnerable to degradation. In the presence of multivalent cations the activation enthalpy for 2M TYMV RNA degradation increased to 150 kJ mol-1 and the entropy of activation to 150 J K-1 mol-1, indicative for a different degradation mechanism.

Cations, Divalent↗
PubMed1997

The ultrastructural localization of 60-kDa Ro protein and human cytoplasmic RNAs: association with novel electron-dense bodies.

The 60-kDa Ro ribonucleoprotein is an important target of humoral autoimmune responses. However, the ultrastructural locations of the 60-kDa Ro protein and its associated small cytoplasmic RNAs (Y RNAs) have not been previously determined, and the functions of the Ro protein and RNAs are not known. In this study, the cellular locations of the 60-kDa Ro protein and the Ro Y1 and Y4 RNAs are determined by immunoelectron microscopy and in situ hybridization electron microscopy, respectively. Both Ro protein and Y RNAs are concentrated in discrete areas of the nucleoplasm, nucleolus, and cytoplasm of cultured cells and human skin sections. The 60-kDa Ro protein and Y RNAs are also present diffusely in the cytoplasm, where they occur in ribosome-rich regions, and in the nucleus. The presence of Ro ribonucleoprotein components in nucleoli and in ribosome-rich cytoplasmic areas suggests a potential for the involvement of Y RNAs and/or 60-kDa Ro protein in ribosome synthesis, assembly, or transport. Double labeling experiments show that Ro protein and Y RNAs colocalize in the nucleoplasm, nucleolus, and cytoplasm. In addition, aggregates of Y RNA occur unassociated with 60-kDa Ro protein, and aggregates of 60-kDa Ro protein occur unassociated with Y RNA. Aggregates of both Ro protein and Y RNAs label previously unreported nuclear and cytoplasmic electron-dense bodies. We propose that these distinctive Ro-associated electron-dense bodies may represent structure(s) important for cellular transport and/or Ro function.

Cell Line↗