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At least 19 recordsLinked to original sources
PubMed1975

Bleomycin: action on growth of oncogenic RNA viruses and on cell transformation.

Bleomycin (BLM) inhibits cell proliferation of noninfected chick embryo fibroblasts by blocking their DNA synthesis selectively. Chick embryo fibroblasts have beentransformed by Schmidt-Ruppin D strain of Rous Sarcoma Virus. Transformation has been determined by a focus assay. Foci formation is strongly reduced by BLM. Virus replication is inhibited by BLM in growing and confluent monolayer cells. This result might be explained by the observation that this drug reduces proliferation of growing and of confluent monolayer cells very sensitively. During the first 24 hours after infection the BLM inhibitory effect is more pronounced than in the case of BLM-application during the period 24--48 hours after infection. This result is explained by published results, showing that cell division is required only for the intitiation of transcription of virus RNA but not for its maintenance. BLM has only little effect on virus growth in transformed cells, because in these cells initiation of transcription of virus RNA has already taken place before the drug was added. From the data obtained it is concluded, that BLM inhibits growth of Rous Sarcoma Virus by blocking cell proliferation.

Animals↗
PubMed1977

Configuration of tobacco mosaic virus, RNA during virus assembly.

When TMV reassembles, the uncoated RNA is folded back along the growing rod, probably down the central hole. This surprising configuration is essential for rapid elongation--presumably supplying RNA to its site of incorporation while keeping the bulk of the free RNA out of the way.

Kinetics↗
PubMed2025

Argonaute 2 targets viral transcripts but not genomes of RNA viruses during antiviral RNA interference in Drosophila.

RNA interference (RNAi) mediated by the small interfering RNA (siRNA) pathway is a major antiviral mechanism in insects. This pathway is triggered when double-stranded RNA (dsRNA) produced during virus replication is recognized by Dicer-2, leading to the formation of virus-derived siRNA duplexes. These siRNAs are loaded onto the programmable nuclease Argonaute-2 (AGO2), with one strand serving as a guide to target and cleave fully complementary sequences of viral RNAs. While siRNAs are generated from viral dsRNA, the specific viral RNA species targeted for silencing during RNA virus replication remains unclear. In this study, we characterized the primary viral RNA targets of the Drosophila siRNA pathway during infections caused by negative and positive RNA viruses, namely Vesicular stomatitis virus (VSV) and Sindbis virus (SINV). Our findings reveal that polyadenylated transcripts of VSV and SINV are the major targets of silencing by the siRNA pathway during infection, likely when they are poised for translation. Consistent with earlier findings, we show that AGO2 is associated with ribosomes in control and virus infected cells. Therefore, we propose that the inhibition of the replication of RNA viruses in Drosophila results from the silencing of incoming viral transcripts, facilitated by the association of AGO2 with ribosomes.

Animals↗
PubMed1977

Strandedness of Pichinde virus RNA.

The Pichinde virus RNA did not possess the following characteristics of eucaryotic mRNA: polyadenylic acid sequence, capped methylated structure, and ability to direct protein synthesis in vitro. Polysomal RNA extracted from cells infected with Pichinde virus reannealed with 32P-labeled virus RNA, protecting about 60% of the latter against RNase degestion. The polyadenylic acid-containing polysomal RNA also reannealed to the 32P-labeled virus RNA to approximately the same extent. These indicate that the major part of the genomic RNA of Pichinde virus is negative stranded.

Arenaviruses, New World↗
PubMed1976

The 30S Moloney sarcoma virus RNA contains leukemia virus nucleotide sequences.

The 50S-70S RNA of a Moloney sarcoma-leukemia virus [Mo-MSV(MLV)] complex produced by a particular mouse cell line was shown by gel electrophoresis to contain a major (97%) 30S sarcoma-specific subunit species and a minor (3%) 38S leukemia virus-specific subunit. On the basis of its sedimentation coefficient and known complexity, the 30S Mo-MSV RNA was estimated to be a unique RNA molecule of about 6000 nucleotides. Hybridization experiments using viral RNA and DNA complementary to viral RNA (cDNA) made by viral DNA polymerase indicated that the 30S Mo-MSV RNA shared 70% of its sequences with Mo-MLV, 30% with another MLV derived from Mo-MLV, and 30% with Kirsten sarcoma-xenotropic leukemia virus. The 30S Mo-MSV RNA sequences shared with these viruses were not additive. The Tm of a Mo-MSV RNA-MLV cDNA hybrid was 83 degrees C, indicating that large contiguous nucleotide sequences were shared between the two nucleic acids. Mo-MSV RNA and Mo-MLV RNA shared possibly seven of 20-30 RNAase T1-resistant oligonucleotides, while Mo-MSV RNA contained three, and Mo-MLV RNA contained at least five specific oligonucleotides. We conclude that the 30S Mo-MSV RNA molecule consists of approximately 70% (about 4200 nucleotides) Mo-MLV-specific sequences and of 30% (1800 nucleotides) Mo-MSV-specific sequences covalently linked. Our results favor the hypothesis that 30S Mo-MSV RNA was generated by recombination between Mo-MLV and other genetic elements. We discuss whether all or only the MSV-specific sequences of the 30S Mo-MSV RNA function as sarcoma genes. Mo-MLV cDNA was hybridized about 45% by unfractionated Mo-MSV (MLV) RNA at RNA/DNA ratios of up to 10, about 50% by electrophoretically purified 30S Mo-MSV RNA at RNA/DNA ratios up to 500, but close to 100% by unfractionated Mo-MSV(MLV) RNA at RNA/DNA ratios over 900. This indicated that unfractionated RNA of our Mo-MSV(MLV) contained a complete complement of Mo-MLV, albeit at a low ratio.

Base Sequence↗
PubMed1979

The effect of pyrophosphate analogues on influenza virus RNA polymerase and influenza virus multiplication.

Analogues of pyrophosphate have been tested as inhibitors of influenza virus-RNA polymerase activity in cell-free assays. The most active compound, phosphonoformic acid (PFA), reduced the polymerase activity to 50 per cent at a concentration of 20 muM. The inhibition was dependent on the type of divalent cation present in the assay. PFA at a concentration of 400 muM also inhibited the influenza virus plaque formation by 90 per cent.

DNA-Directed RNA Polymerases↗
PubMed1978

Photochemical inactivation of DNA and RNA viruses by psoralen derivatives.

Western equine encephalitis virus, and RNA virus, and herpes simplex virus type I, a DNA virus, were efficiently inactivated in less than I min by exposure to long-wave ultraviolet light (320 to 380 nm) in the presence of several psoralen derivatives. The psoralen photochemical reaction was chosen for study due to its known specificity for nucleic acids. Neither the light nor any of the drugs alone caused appreciable inactivation. The inactivation kinetics and dependence on light intensity and on different derivatives of psoralen were studied. The high solubility of a new aminomethyl psoralen derivative was found to be advantageous in the photochemical inactivation of the RNA virus, but was not in the case of the more easily inactivated DNA virus. Within its limited solubility range trimethylpsoralen was superior to its aminomethyl derivative on a molar basis for the inactivation of both types of viruses under most of the conditions studied.

Cell Line↗
PubMed1976

Increased sarcoma virus RNA in cells transformed by leukemia viruses: model for leukemogenesis.

A morphologically flat revertant of mink cells nonproductively infected with Moloney sarcoma virus exhibited contact inhibition and lacked detectable sarcoma virus RNA. Superinfection by usually nontransforming type C mammalian leukemia-causing viruses induced transformation and increased sarcoma virus RNA. The results suggest a model for leukemogenesis in animals by increasing, during replication of usually nontransforming leukemia viruses, the levels of RNA from potentially oncogenic cell or integrated virus transforming genes.

Cell Transformation, Neoplastic↗
PubMed1976

Size and location of poly (A) in encephalomyocarditis virus RNA.

Encephalomyocarditis (EMC) virus RNA contains a covalently bound sequence of polyriboadenylic acid (poly(A). This was determined by two-dimensional gel electrophoresis of complete T1 and pancreatic RNase digests of formamidesucrose gradient-purified RNA and subsequent analysis of the product by alkaline hydrolysis. The size of the EMC virus genomic poly(A) sequence was estimated by formamide-polyacrylamide gel electrophoresis of the RNase-resistant product, or by [3H-]poly(U) hybridization to freshly purified virion RNA, to be, on average, 40 nucleotides in length. The evidence obtained from [3H-]isoniazid labelling and other experiments would indicate that the poly(A) sequence is located at the 3'-terminus of EMC virus RNA.

Base Sequence↗
PubMed1977

Extensive in vitro transcription of rous sarcoma virus RNA by avian myeloblastosis virus DNA polymerase and concurrent activation of the associated RNase H.

Conditions are described that promote the efficient reverse transcription of most of Rous sarcoma virus (RSV) RNA sequences by avian myeloblastosis virus DNA polymerase in vitro. A detailed analysis of the reverse transcription reaction was carried out using two procedures: in situ analysis of the RNA sequences transcribed and DNA-RNA annealing studies. Under optimal conditions, after 1 h of reaction, practically all RSV RNA sequences were transcribed with a frequency varying from 30 to 90%. The DNA product was at least 95% single stranded, had a chain length ranging from a few hundred up to 5,000 necleotide residues, half of it being larger than 1,000 residues, and, after hybridization at RNA excess, protected the entire RSV genome from RNase digestion, as monitored by the large T1 oligonucleotides of RSV RNA. Analysis of the product of a very short reaction time (5 min) showed that DNA synthesis occurs mainly at three sites, one near the 5' end and two near the center of the subunit RNA. This in in agreement with our previous analysis of a much less efficient reverse transcription reaction. Under optimal conditions of reverse transcription, we find now that the RNase H associated with the avian myeloblastosis virus DNA polymerase is active in degrading the RNA moiety of the RNA-DNA hybrids synthesized.

Avian Leukosis Virus↗
PubMed1977

The size and location of the poly(A) tract in EMC virus RNA.

Encephalomyocarditis (EMC) virus RNA, selected by its affinity for oligo(dT)-cellulose, contains poly(A) of size : (i) about 14 nucleotide residues long, based on the percentage of radioactivity in the RNA resistant to digestion by a mixture of pancreatic and T1 RNases; (ii) about 15 residues long, as measured by the ratio of the amount of terminal adenosine to internal adenylic acid in isolated poly(A); and (III) in the range 12 to 45 residues, the majority of tracts being about 16 to 18 residues long, based upon electrophoretic mobility on polyacrylamide gels using poly(A) molecules of known size as mol. wt. markers. The poly(A) appears to be located at the 3'-terminus of the virus genome since the tract, liberated by digestion with a mixture of pancreatic and T1 RNases, was shown by compositional analysis to contain a non-phosphorylated 3'-terminus and only adenine residues. The size heterogeneity in the poly(A) tracts revealed by gel electrophoresis is also consistent with a terminal location. Comparison of our data for EMC virus with published data for other picornaviruses suggests that the sizes of poly(A) tracts in polio- and Mengovirus RNA have been overestimated; poly(A) tracts in cardioviruses appear to be smaller than those in poliovirus; the minimum size of poly(A) required for full infectivity of picornavirus RNA has also been overestimated; a tract of at least 13 adenine residues long is required for full infectivity of EMC virus RNA.

Base Sequence↗
PubMed1979

The nucleotide sequence at the 5' end of foot and mouth disease virus RNA.

Foot and mouth disease virus RNA has been treated with RNase H in the presence of oligo (dG) specifically to digest the poly(C) tract which lies near the 5' end of the molecule (10). The short (S) fragment containing the 5' end of the RNA was separated from the remainder of the RNA (L fragment) by gel electrophoresis. RNA ligase mediated labelling of the 3' end of S fragment showed that the RNase H digestion gave rise to molecules that differed only in the number of cytidylic acid residues remaining at their 3' ends and did not leave the unique 3' end necessary for fast sequence analysis. As the 5' end of S fragment prepared form virus RNA is blocked by VPg, S fragment was prepared from virus specific messenger RNA which does not contain this protein. This RNA was labelled at the 5' end using polynucleotide kinase and the sequence of 70 nucleotides at the 5' end determined by partial enzyme digestion sequencing on polyacrylamide gels. Some of this sequence was confirmed from an analysis of the oligonucleotides derived by RNase T1 digestion of S fragment. The sequence obtained indicates that there is a stable hairpin loop at the 5' terminus of the RNA before an initiation codon 33 nucleotides from the 5' end. In addition, the RNase T1 analysis suggests that there are short repeated sequences in S fragment and that an eleven nucleotide inverted complementary repeat of a sequence near the 3' end of the RNA is present at the junction of S fragment and the poly(C) tract.

Aphthovirus↗
PubMed1978

Autoregulation of adenovirus type 5 early gene expression II. Effect of temperature-sensitive early mutations on virus RNA accumulation.

The kinetics of accumulation of early virus RNA in the cytoplasm of KB cells infected at 40.5 degrees C by wild-type (WT) adenovirus type 5 and a temperature-sensitive "early" mutant, H5ts125 (ts125), were compared by hybridization of unlabeled RNA in solution to the (3)H-labeled l strand of Ad5 DNA HindIII restriction endonuclease fragment A. In the presence of 1-beta-d-arabinofuranosylcytosine, A(l) RNA accumulated in WT-infected cells for 9 h and then decreased in concentration to 6% of the 9-h concentration by 18 h. In ts125-infected cells, A(l) RNA accumulated for 12 h and then remained at the same concentration for at least 6 h thereafter. The concentrations of virus RNA from the four early transcription regions of the genome were measured at 15 h in cells infected at 40.5 degrees C in the presence of 1-beta-d-arabinofuranosylcytosine by: (i) ts125 and WT; (ii) two other ts early mutants, ts107 and ts149; and (iii) a revertant of ts125. The revertant and ts149, a mutant from a different complementation group than ts125, both accumulated all early virus cytoplasmic RNA species in amounts similar to, or less than, WT. However, both ts125 and ts107, independently isolated mutations in the 72,000-molecular-weight (72K) DNA-binding protein gene, accumulated cytoplasmic early RNA in excess of that found in WT infection. This pattern of RNA accumulation with the mutants and WT virus was the same in the nuclei as in the cytoplasm at 40.5 degrees C. At 32 degrees C, however, the abundance of nuclear virus RNA from all four early regions was the same in cells infected by either ts125 or WT. Differences in the relative abundance of nuclear RNA from the four early regions were observed in cells infected at 40.5 and 32 degrees C, but were not dependent upon the infecting virus genotype. These results are consistent with autoregulation of early gene expression by the 72K protein and support the hypothesis that the 72K protein either decreases the rate of early virus transcription or increases the rate of virus RNA degradation in the nucleus.

Adenoviruses, Human↗