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At least 19 recordsLinked to original sources
PubMed2001

Signal peptides bind and aggregate RNA. An alternative explanation for GTPase inhibition in the signal recognition particle.

N-terminal signal sequences can direct nascent protein chains to the inner membrane of prokaryotes and the endoplasmic reticulum of eukaryotes by interacting with the signal recognition particle. In this study, we show that isolated peptides corresponding to several bacterial signal sequences inhibit the GTPase activity of the Escherichia coli signal recognition particle, as previously reported (Miller, J. D., Bernstein, H. D., and Walter, P. (1994) Nature 367, 657-659), but not by the direct mechanism proposed. Instead, isolated signal peptides bind nonspecifically to the RNA component and aggregate the entire signal recognition particle, leading to a loss of its intrinsic GTPase activity. Surprisingly, only "functional" peptide sequences aggregate RNA; the peptides in general use as "nonfunctional" negative controls (e.g. those with deletions or charged substitutions within the hydrophobic core), are sufficiently different in physical character that they do not aggregate RNA and thus have no effect on the GTPase activity of the signal recognition particle. We propose that the reported effect of functional signal peptides on the GTPase activity of the signal recognition particle is an artifact of the high peptide concentrations and low salt conditions used in these in vitro studies and that signal sequences at the N terminus of nascent chains in vivo do not exhibit this activity.

GTP Phosphohydrolases↗
PubMed1977

RNA aggregation during sulfhydryl-agarose chromatography of mercurated RNA.

Isolation of newly synthesized mercurated RNA transcripts by chromatography on sulfhydryl-agarose has recently been used to reduce contamination by endogenous RNA derived from the chromatin template. We show that substantial RNA aggregation occurs during standard isolation procedures, causing significant retention of endogenous (unmercurated) RNA on sulfhydryl-agarose. We describe methods to reduce substantially this problem and discuss the implications of our findings for interpretation of previous hybridization and transcription experiments.

Animals↗
PubMed1989

The fetal blood erythrocyte micronucleus assay: classification of RNA-positive erythrocytes into two age populations by RNA aggregation state.

The use of a fluorescent stain containing Hoechst 33258 and pyronin Y in the fetal mouse transplacental micronucleus assay allows classification of erythrocytes into three subpopulations on the basis of RNA staining, and permits micronuclei to be scored in all three subpopulations. The youngest erythrocytes stain uniformly positive for RNA (UEs). In older erythrocytes RNA aggregates to give the cells a stippled appearance (SEs) and ultimately disappears, leaving cells which do not stain positively for RNA. Frequencies of micronucleated UEs and SEs were determined at 30 and 48 h following a single dose of methyl methanesulfonate, benzo[a]pyrene, lasiocarpine, monocrotaline or heliotrine. With each agent and dose tested, the frequency of micronuclei increased first in the younger UEs and later in SEs. The use of the Hoechst/pyronin staining procedure, which permits DNA to be distinguished from RNA, minimizes the potential for mis-scoring RNA artefacts as micronuclei and also increases the efficiency of the assay by permitting two age populations of erythrocytes to be scored in each sample.

Animals↗
PubMed1975

Isolation of RNA transcripts from the entire Sendai viral genome.

Three classes of viral transcripts (18S, 24S, and 33S) were isolated from viral ribonucleoproteins in Sendai virus-infected cells. Hybridization studies with virion minus strand genome RNA demonstrated that the 18S RNA contained transcripts from 60% of the viral genome while the 33S RNA contained transcripts from the entire viral genome. Brief heat of ME2SO treatment of the 33S RNA demonstrated that this RNA was composed of two classes: RNA which continued to sediment at 33S (33S RNA) and 18S RNA aggregates (18S RNA). The 33S RNA was determined to be a transcript from the 40% of the viral genome not protected by the 18S RNA. The aggregated 18S RNA does not appear to be an artifact of isolation.

Culture Techniques↗
PubMed2006

Model for folding and aggregation in RNA secondary structures.

We study the statistical mechanics of RNA secondary structures designed to have an attraction between two different types of structures as a model system for heteropolymer aggregation. The competition between the branching entropy of the secondary structure and the energy gained by pairing drives the RNA to undergo a "temperature independent" second order phase transition from a molten to an aggregated phase. The aggregated phase thus obtained has a macroscopically large number of contacts between different RNAs. The partition function scaling exponent for this phase is theta approximately 1/2 and the crossover exponent of the phase transition is nu approximately 5/3. The relevance of these calculations to the aggregation of biological molecules is discussed.

Models, Chemical↗
PubMed1996

The activity on double-stranded RNA of aggregates of ribonuclease A higher than dimers increases as a function of the size of the aggregates.

Stable bovine RNase A aggregates larger than dimers (identified as trimers, tetramers, pentamers and hexamers) were obtained by lyophilization of RNase A from 40-50% acetic acid solutions. The RNase activity of these aggregates was compared with that of monomeric RNase A on single- and double-stranded polyribonucleotides. Their activity toward poly(U) and yeast RNA slightly decreases as a function of the size of the aggregates. In contrast, their action on poly(A).poly(U) as substrate progressively increases from a relative activity of 1 for the RNase monomer to 10 for the hexamer. These results are discussed in the light of an already advanced hypothesis about a possible mechanism of RNase attack on double-stranded RNA.

Animals↗
PubMed1996

RNA stimulates aggregation of microtubule-associated protein tau into Alzheimer-like paired helical filaments.

The microtubule-associated protein tau is the main component of the paired helical filaments (PHFs) of Alzheimer's disease, the most common senile dementia. To understand the origin of tau's abnormal assembly we have studied the influence of other cytosolic components. Here we report that PHF assembly is strongly enhanced by RNA. The RNA-induced assembly of PHFs is dependent on the formation of intermolecular disulfide bridges involving Cys322 in the third repeat of tau, and it includes the dimerization of tau as an early intermediate. Three-repeat constructs polymerize most efficiently, two repeat constructs are the minimum number required for assembly, and even all six full-length isoforms of tau can be induced to form PHFs by RNA.

Alzheimer Disease↗
PubMed1981

Effect of 3-methylcholanthrene administration on hepatic ribonucleic acid polymerase activities.

The effect of the in vivo administration of 3-methylcholanthrene upon rat hepatic RNA polymerase activities was investigated. Aggregate RNA polymerase activity assayed in liver nuclei was stimulated by 33% over control. Characterization of the individual RNA polymerase activities by virtue of their differential sensitivity to alpha-amanitin revealed that RNA polymerase I activity was maximally increased by 70% at approx. 16 h post-administration of the polycyclic hydrocarbon; RNA polymerase II activity was stimulated by 33%. The kinetics of RNA polymerases I and II stimulation differed in that the nucleolar enzyme's activity increased earlier and peaked later. RNA polymerase III activity was not significantly different from control. Phenobarbital, another inducer of the mixed function oxidases, had essentially no effect on the activity of hepatic RNA polymerases. Solubilization of the RNA polymerases followed by separation on diethylaminoethyl (DEAE)-Sephadex allowed for a comparison of the treated and control enzymatic activities using a common exogenous template. While no qualitative difference was evident, RNA polymerases I and II isolated from 3-methylcholanthrene-treated rats again were more active than control, indicating an effect of the polycyclic hydrocarbon at the level of the enzyme.

Animals↗
PubMed1977

Frog oocytes synthesize and completely process the precursor polypeptide to virion structural proteins after microinjection of avian myeloblastosis virus RNA.

After microinjection of Xenopus laevis oocytes with RNA from avian myeloblastosis virus, viral structural proteins p27, p19, p15, and p12 are formed by a sequence of posttranslational cleavages of a high-molecular-weight precursor polypeptide. The 60-70S RNA aggregate or its 30-40S RNA subunits obtained by heat or formamide treatment possess the same ability to serve as template in X. laevis oocytes. The processing pattern of virus-specific precursor polypeptides is the same in X. laevis oocytes as in chick embryo fibroblasts infected with avian myeloblastosis virus, but the processing takes place at a much slower rate.

Animals↗
PubMed1976

[Isolation of RNA containing a polyadenylic acid sequence by chromatography on unmodified cellulose].

A new modification of the procedure of the isolation of polyA-containing RNAs is worked out, which makes possible to isolate this RNA fraction free of considerable contamination with rRNA. The administration of 0.0001 M EDTA-Na2 provides the absence of RNA aggregation and prevents non-specific RNA binding on cellulose columns, which takes place when more high EDTA-Na2 concentrations in elution solutions are applied. Under these conditions synthetic polyA in model experiments practically completely binds with cellulose in a broad range of concentrations. It permits to use the procedure described for the preparative isolation of RNA fractions, containing polyA sequences.

Animals↗