Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Early chicken embryos that are either positive or negative for group-specific antigens of avian leukosis viruses contained endogenous RNA-directed DNA polymerase activity. This endogenous DNA polymerase activity was not increased after mixture of soluble DNA polymerases isolated from chicken embryos with disrupted chicken embryo cells. The endogenous activity was resistant to treatment with deoxyribonuclease, and the initial rate of DNA synthesis was partially resistant to actinomycin D. In contrast, over 90% of the endogenous polymerase activity was destroyed by ribonuclease in medium with high salt concentration. The DNA product of the endogenous DNA polymerase activity from chicken embryos did not hybridize with RNA of Rous sarcoma virus or reticuloendotheliosis virus, whereas about 40% of this DNA product hybridized with the RNA from the same chicken-cell fraction. Antibody against DNA polymerase of avian myeloblastosis virus did not neutralize the chicken endogenous DNA polymerase activity. These results demonstrate that uninfected chicken embryo cells contain endogenous RNA-directed DNA polymerase activity that is not derived from avian leukosis or reticuloendotheliosis viruses.
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PMID:Endogenous RNA-directed DNA polymerase activity in uninfected chicken embryos. 433 97

A sensitive and quantitative nucleic acid hybridization assay for the detection of radioactively labeled avian tumor virus-specific RNA in infected chicken cells has been developed. In our experiments we made use of the fact that DNA synthesized by virions of avian myeloblastosis virus in the presence of actinomycin D (AMV DNA) is complementary to at least 35% of the sequences of 70S RNA from the Schmidt-Ruppin strain (SRV) of Rous sarcoma virus. Annealing of radioactive RNA (either SRV RNA or RNA extensively purified from SRV-infected chicken cells) with AMV DNA followed by ribonuclease digestion and Sephadex chromatography yielded products which were characterized as avian tumor virus-specific RNA-DNA hybrids by hybridization competition with unlabeled 70S AMV RNA, equilibrium density-gradient centrifugation in Cs(2)SO(4) gradients, and by analysis of their ribonucleotide composition. The amount of viral RNA synthesized during pulse labeling with (3)H-uridine could be quantitated by the addition of an internal standard consisting of (32)P-labeled SRV RNA prior to purification and hybridization. This quantitative assay was used to determine that, in SRV-infected chicken cells labeled for increasing lengths of time with (3)H-uridine, labeled viral RNA appeared first in a nuclear fraction, then in a cytoplasmic fraction, and still later in mature virions. This observation is consistent with the hypothesis that RNA tumor virus RNA is synthesized in the nucleus of infected cells.
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PMID:Quantitative determination and location of newly synthesized virus-specific ribonucleic acid in chicken cells infected with Rous sarcoma virus. 435 Jul 19

Two low-molecular-weight RNAs are associated with the 70S RNA complex of Rous sarcoma virus: a previously described 4S RNA and a newly identified 5S RNA. The 4S RNA constitutes 3 to 4% of the 70S RNA complex or the equivalent of 12 to 20 molecules per 70S RNA. It exhibits a number of structural properties characteristic of transfer RNA as revealed by two-dimensional electrophoresis of oligonucleotides obtained from a T1 ribonuclease digest of the 4S RNA species. The 5S RNA is approximately 120 nucleotides in length, constitutes 1% of the 70S RNA complex or the equivalent of 3 to 4 molecules per molecules of 70S RNA, and is identical in nucleotide composition and structure to 5S RNA from uninfected chicken embryo fibroblasts. Melting studies indicate that the 5S RNA is released from the 70S RNA complex at the same temperature required to dissociate 70S RNA into its constituent 35S subunits. In contrast, greater than 80% of the 4S RNA is released from 70S RNA prior to its conversion into subunits. The possible biological significance of these 70S-associated RNAs is discussed.
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PMID:Characterization of the low-molecular-weight RNAs associated with the 70S RNA of Rous sarcoma virus. 435 35

Approximately 15 to 20 different species of small (4 to 7S) RNAs have been purified by two-dimensional polyacrylamide gel electrophoresis of RNA isolated from virions of Schmidt-Ruppin D strain of Rous sarcoma virus. Each species of small RNA has been isolated free of 70S RNA; nine of them, including 5S and 7S RNAs, were also found associated with the 70S genomic RNA. Most of the 4S RNAs are present at an average of less than one copy per virion. The 4S RNAs have T1 RNase (EC 2.7.7.26) fingerprints, which are very similar to those of tRNAs. One of the smallest 4S RNAs, which can act as a primer for initiation of RNA-directed DNA synthesis, is associated with the 70S RNA in 1 to 2 copies per complex, whereas an additional 6 to 8 copies of this molecule are free.
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PMID:Small RNAs of Rous sarcoma virus: characterization by two-dimensional polyacrylamide gel electrophoresis and fingerprint analysis. 435 5

Earlier electrophoretic analyses have shown that the 60-70S RNA of avian sarcoma viruses contains a characteristic subunit, termed class a subunit, which has a lower electrophoretic mobility than class b subunit found in transformation-defective derivatives of sarcoma viruses and in avian leukosis viruses. We have compared the RNAs of three nondefective avian sarcoma viruses, B77 and Prague and Schmidt-Ruppin strains of Rous sarcoma virus, with those of their transformation-defective (td) derivatives, td B77, td PR-C, and td SR-A, respectively, to determine the chemical basis for the difference between class a and b subunits. It was found by "fingerprinting" that (1) all (about 20-25) large T1 RNase-resistant oligonucleotides present in class b subunits of transformation-defective viruses have homologous counterparts in the class a subunits of corresponding nondefective sarcoma viruses and that (2) class a subunits contain a few (one or two) additional oligonucleotides that are not present in class b. By contrast the oligonucleotide fingerprints of avian tumor viruses of different strains and subgroups were very different.Cross hybridization of classes a and b RNA of sarcoma virus B77 with DNA transcribed from a corresponding transformation-defective virus td B77 showed that the two RNAs share at least 60% and differ by about 10% of their sequences. It is suggested that the structural relationship of class a and b subunits of corresponding viruses may be expressed as a = b + x, and that all the oligonucleotides present only in RNAs of sarcoma viruses but not in transformation-defective viruses of the corresponding strains are part of sequence(s) x. The possibility that x represents genetic information directly or indirectly involved in transformation of fibroblasts is discussed.
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PMID:Avian tumor virus RNA: a comparison of three sarcoma viruses and their transformation-defective derivatives by oligonucleotide fingerprinting and DNA-RNA hybridization. 436 99

The poly(A) sequence of 30 to 40S Rous sarcoma virus RNA, prepared by digestion of the RNA with RNase T(1), showed a rather homogenous electrophoretic distribution in formamide-polyacrylamide gels. Its size was estimated to be about 200 AMP residues. The poly(A) appears to be located at or near the 3' end of the 30 to 40S RNA because: (i) it contained one adenosine per 180 AMP residues, and because (ii) incubation of 30 to 40S RNA with bacterial RNase H in the presence of poly(dT) removed its poly(A) without significantly affecting its hydrodynamic or electrophoretic properties in denaturing solvents. The viral 60 to 70S RNA complex was found to consist of 30 to 40S subunits both with (65%) and without (approximately 30%) poly(A). The heteropolymeric sequences of these two species of 30 to 40S subunits have the same RNase T(1)-resistant oligonucleotide composition. Some, perhaps all, RNase T(1)-resistant oligonucleotides of 30 to 40S Rous sarcoma virus RNA appear to have a unique location relative to the poly(A) sequence, because the complexity of poly(A)-tagged fragments of 30 to 40S RNA decreased with decreasing size of the fragment. Two RNase T(1)-resistant oligonucleotides which distinguish sarcoma virus Prague B RNA from that of a transformation-defective deletion mutant of the same virus appear to be associated with an 11S poly(A)-tagged fragment of Prague B RNA. Thus RNA sequences concerned with cell transformation seem to be located within 5 to 10% of the 3' terminus of Prague B RNA.
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PMID:Properties and location of poly(A) in Rous sarcoma virus RNA. 437 9

The nucleotide sequence complexity of 60-70S RNA of Rous sarcoma virus was determined from the molar yields of 11 pure oligonucleotides of known chain length, obtained from [(32)P]RNA of Rous sarcoma virus by T1 RNase digestion and two-dimensional polyacrylamide gel electrophoresis. We calculate an apparent chain length of about 9800 nucleotides, corresponding to a molecular weight of 3.4 x 10(6). Assuming the molecular weight of 60-70S RNA of Rous sarcoma virus to be about 10(7), our data suggest that the virus genome consists of identical, or very similar, nucleotide sequences repeated three to four times.
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PMID:The nucleotide sequence complexity of avian tumor virus RNA. 437 25

We previously reported that in the endogenous reaction of Rous sarcoma virus disrupted by melittin, plus-strand DNA initiates on a small oligonucleotide primer and that this initiation can be reconstructed in vitro in reactions containing purified minus-strand DNA as template, viral RNA as a source of primer, and reverse transcriptase (Smith et al., J. Virol. 49:200-204, 1984). Further studies on the specificity of initiation in the endogenous reaction have shown the following. (i) The primer was 12 nucleotides in length. Its sequence began with a 5' pyrimidine, followed by 11 purines, ending with rGrA-3'. This sequence was in agreement with the known plus-strand RNA sequence immediately upstream from the initiation site. Thus, the primer began one nucleotide 5' to the so-called polypurine tract that has been found on all retrovirus genomes. (ii) The transition point between RNA primer and DNA product was precisely located. It was before the end of the polypurine tract. Thus the polypurine tract, although essential for virus replication and probably a flag for the priming event, did not define the limits of the RNA primer. After primer removal, the DNA had a 5' phosphate, consistent with generation by the viral RNase H activity. The priming specificity in reconstructed reactions was also examined further, with the following observations. (i) When the source of RNA primer was prehybridized to the template viral DNA, the generation, utilization, and subsequent removal of primer were essentially the same as those observed in the endogenous reaction. In the absence of deliberate prehybridization, some specificity was lost. There were than additional locations for the 5' end of the primer as well as the transition point between RNA primer and DNA. (ii) Purine-rich oligoribonucleotides created by RNase A digestion of viral RNA could prime strong-stop plus DNA, but again with the loss of specificity relative to that in the endogenous reaction. (iii) The 5' end of the minus-strand DNA template was not required for initiation of strong-stop plus DNA. Therefore, the specificity of initiation did not depend upon an intramolecular interaction requiring the two inverted repeat sequences that flank the long terminal repeat.
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PMID:Specificity of initiation of plus-strand DNA by Rous sarcoma virus. 609 61

Several methods were used for isolation of double-stranded (ds) RNA from the cytoplasm of Rous sarcoma virus-transformed chick embryo cells. The dsRNA was shown to have a high melting temperature (82.5 degrees C) in 0.16 M phosphate buffer (pH 6.8), which shifted to more than 90 degrees C after RNase treatment. The size of a single strand was approximately 1300-1600 nucleotides and RNase-resistant fragments were 50-250 nucleotides long. Double-stranded RNA formed hybrids with the labeled genomic RSV RNA RNA so that the major subpopulation of the dsRNA hybridized to 6-10% of RSV RNA and the minor subpopulation -- to 90-94% of RSV RNA. It was suggested that this large subpopulation of dsRNA was abundant in sequences homologous to proviral end fragments as judged by Southern procedure. The data are discussed by considering the analogy between retroviral proviruses and mobile genetic elements.
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PMID:[Isolation of virus-specific double-stranded RNA from cells transformed with Rous sarcoma virus]. 609 11

The secondary structure of avian myeloblastosis virus (AMV) RNA was characterized by electron microscopy under moderately denaturing spreading conditions. Under denaturation by aqueous 44% formamide or 77% formamide in the presence of salts, partly stretched RNA molecules with measurable double-stranded regions were observed. This approach allowed the localization from 5 to 11 regions of preserved secondary structure on AMV RNA molecules. Topographic analysis revealed a nonrandom occurrence of stable secondary structures in several prevalent regions. These regions with higher secondary structure stability revealed certain similarity to hairpin structures localized by electron microscopy on Rous sarcoma virus RNA or to highly structured regions found on this RNA by T1 ribonuclease oligonucleotide analysis.
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PMID:Studies on the structure of avian myeloblastosis virus (AMV) RNA. III. Electron microscopic definition of secondary structure. 612 7


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