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:3.1.27.3 (RNase T1)
1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
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PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

A method for the isolation of RNA fragments originating from defined regions of bacteriophage Qbeta RNA minus strands is described. Large RNase T1 oligonucleotides were isolated on a preparative scale from Qbeta RNA. The nucleotide sequences (13 to 26 nucleotides) and map positions of these oligonucleotides were known from previous work (Billeter, M. A. (1978) J. Biol. Chem. 253, 8381-8389). After addition of AMP residues (50 in the average) using terminal adenylate transferase, these pure oligonucleotides were hybridized to 32P-labeled Qbeta RNA minus strands synthesized in vitro. Fragments in the size range of 100 to 500 nucleotides were then generated by partial digestion with RNase T1. Fragments hybridized to such oligonucleotides were recovered by chromatography on poly(U)-Sephadex and then resolved according to their size by polyacrylamide gel electrophoresis. The specificity and reproducibility of the method as well as its suitability for the sequence analysis of Qbeta RNA was verified by using in particular a linker oligonucleotide derived from a Qbeta RNA region near the 3' end. The sequence catalogues of the RNase T1 and RNase A oligonucleotides of two fragments isolated in this way, 202 and 310 nucleotides in length, were established and all fragments isolated were shown to contain a sequence complementary to the linker oligonucleotide.
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PMID:A hybridization procedure for the isolation of specific RNA segments applied to the analysis of bacteriophage Qbeta RNA. 10 41

The nucleotide sequence of formylmethionine tRNA from an extreme thermophile, Thermus thermophilus HB8, was determined by a combination of classical methods using unlabeled samples to determine the sequences of the oligonucleotides of RNase T1 and RNase A digests and a rapid sequencing gel technique using 5'-32P labeled samples to determine overlapping sequences. Formylmethionine tRNA from T. thermophilus is composed of two species, tRNAf1Met and tRNAf2Met. Their nucleotide sequences are almost identical, and are also almost identical with that of E. coli tRNAfMet, except for slight modifications and replacements. Both species have modifications at three points which do not exist in E. coli tRNAfMet: 2'-O-methylation at G19, N-1-methylation at A59 and 2-thiolation at T55. Moreover U51 in E. coli tRNAfMet is replaced by C51 in both species, so that a G-C pair is formed between this C51 and G65. tRNAf2Met has a reversed G-C pair at positions 52 and 64 compared with those in tRNAf1Met and E. coli tRNAfMet. Other regions are mostly the same as those in all prokaryotic initiator tRNAs so far reported. The thermostability of these thermophile initiator tRNAs is discussed in relation to their unique modifications.
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PMID:Nucleotide sequence of formylmethionine tRNA from an extreme thermophile, Thermus thermophilus HB8. 11 55

Incubation of Neurospora crassa conidia with ribonuclease (RNase) A reduces transport of L-phenylalanine by those cells. Under similar conditions, oxidized RNase A, RNase T1, and RNase T2 do not have this effect. Incubation of conidia with active RNase covalently attached to polyacrylamide beads reduces L-phenylalanine transport. This indicates that the site of enzymatic action is at the cell surface. At the lower concentration of enzyme used in this study, incubation with RNase A reduces transport of L-phenylalanine by the general (G) amino acid permease. Increasing the enzyme concentration results in reduction of transport by the neutral aromatic (N)-specific permease. The increased transport activity that accompanies onset of conidial germination is also sensitive to incubation with RNase A. Application of the enzyme to actively transporting cells does not release amino acid transported prior to enzyme addition. Cells cultured on media supplemented with [2-14C] uridine release isotopic activity after RNase A incubation. Analogous treatments with Pronase, RNase T1, RNase T2, or deoxyribonuclease I do not release isotope activity. Pronase treatment does reduce L-phenylalanine transport. Incubation of conidia with RNase A also inhibits germination of those conidia.
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PMID:Effects of ribonuclease A on amino acid transport in Neurospora crassa. 12 24

The RNA of a replication-defective (rd) mutant, isolated from stocks of nondefective (nd) Schmidt-Ruppin Rous sarcoma virus of subgroup A (SR-A) and termed SR-N8, was compared to the RNAs of SR-A, of a transformation-defective derivative of SR-A (td SR-A) and of rd Bryan Rous sarcoma virus, RSV (minus). The molecular mass of the 30-40S species of SR-N8 RNA was estimated to be 21% (congruent to 7.5 to 8 times 10-5 daltons) smaller than that of SR-A by (i) electrophoresis in polyacrylamide gels and (ii) analyses of RNA complexity based on RNase T1-resistant oligonucleotides. ST-N8 shares probably all (=14) of its large RNase T1-resistant oligonucleotides with the RNA of SR-A as judged from the chromatographic distribution and the RNase A-resistant fragments obtained from RNase T1-resistant oligonucleotides. However, SR-N8 RNA lacked six large oligonucleotides which were present in the RNAs of SR-A and td SR-A. Conversely, the RNAs of SR-A, and of SR-N8 contained two oligonucleotides not found in td SR-A. The RNA of SR-N8 was found to differ from that of RSV (minus) in its electrophoretic mobility and its fingerprint pattern. It is concluded that the RNA of SR-N8 was generated by a deletion of SR-A. The extent of this deletion is compatible with the notion that the genetic information for the large viral envelope glycoprotein (molecular mass = 70,000-85,000 daltons) has been lost from the RNA of SR-A to yield SR-N8 RNA. From a comparison of td and rd deletion mutants, it appears that loss of different functions corresponds to the absence of different oligonucleotides in their RNA.
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PMID:RNA of replication-defective strains of Rous sarcoma virus. 16 14

The large RNase T1-resistant oligonucleotides of the nondefective (nd) Rous sarcoma virus (RSV): Prague RSV of subgroup B (PR-B), PR-C and B77 of subgroup C; of their transformation-defective (td0 deletion mutants: td PR-B, td PR-C, and td B77; and of replication-defective (rd) RSV(-) were completely or partially mapped on the 30 to 40S viral RNAs. The location of a given oligonucleotide relative to the poly(A) terminus of the viral RNAs was directly deduced from the smallest size of the poly(A)-tagged RNA fragment from which it could be isolated. Identification of distinct oligonucleotides was based on their location in the electrophoretic/chromatographic fingerprint pattern and on analysis of their RNase A-resistant fragments. The following results were obtained. (i) The number of large oligonucleotides per poly(A)-tagged ffagment increased with increasing size of the fragment. This implies that the genetic map is linear and that a given RNase T1-resistant oligonucleotides has, relative to the poly(A) end, the same location on all 30 to 40S RNA subunits of a given 60 to 70S viral RNA complex, (ii) Three sarcoma-specific oligonucleotides were identified in the RNAs of Pr-B, PR-C and B77 by comparison with the RNAs of the corresponding td viruses...
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PMID:Mapping RNase T1-resistant oligonucleotides of avian tumor virus RNAs: sarcoma-specific oligonucleotides are near the poly(A) end and oligonucleotides common to sarcoma and transformation-defective viruses are at the poly(A) end. 17 Apr 11

The genetic complexities of several ribodeoxyviruses were measured by quantitative analysis of unique RNase T1-resistant oligonucleotides from 60-70S viral RNAs. Moloney murine leukemia virus was found to have an RNA complexity of 3.5 x 10(6) daltons, whereas Moloney murine sarcoma virus had a significantly smaller genome size of 2.3 x 10(6). Reticuleondotheliosis and visna virus RNAs had complexities of 3.9 x 10(6), respectively. Analysis of RNase A-resistant oligonucleotides of Rous sarcoma virus RNA gave a complexity of 3.6 x 10(6), similar to that previously obtained with RNase T1-resistant oligonucleotides. Since each of these viruses was found to have a unique sequence genomic complexity near the molecular weight of a single 30-40S viral RNA subunit, it was concluded that ribodeoxyvirus genomes are at least largely polyploid.
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PMID:Genomic complexities of murine leukemia and sarcoma, reticuloendotheliosis, and visna viruses. 17 29

Current studies were undertaken to compare the genomes of Kirsten murine sarcoma virus (Ki-MuSV), Harvey murine sarcoma virus (Ha-MuSV), and the replication-defective endogenous rat virus to understand the function of these viral RNAs. Genome organization and sequence homology were studied by fingerprinting large RNase T1-resistant oligonucleotides and by cross-protecting homologous oligonucleotides against RNase A and T1 digestion with complementary DNA prepared from each of the other viral RNA. Ki-MuSV and Ha-MuSV were found to share an extensive series of rat-derived oligonucleotides begining ca. 1 kilobase (kb) from the 3' end and extending to within 1.5 kb of the 5'end of Ki-MuSV RNA. The total map distance covered in ca. 5.5 kb. The eight oligonucleotides covering the 1.5 kb at the 5' end of Ki-MuSV RNA were not found in Ha-MuSV RNA. Five out of these eight oligonucleotides, however, could be designated with certainty to be of rat virus origin. Since Ha-MuSV is 6.5 kb in size and Ki-MuSV is 8 kb in size, the major difference between them is the 1.5 kb from the replication-defective endogenous rat virus sequences at the 5' end of Ki-MuSV not present in Ha-MuSV. Consistent with the difference in the genome structure, these two sarcoma viral RNA'S yielded distinct major translation products in cell-free systems, I.E., A 50,000-dalton polypeptide (P50) from Ki-MuSV and a 22,000-dalton polypeptide (p22) from Ha-MuSV. These polypeptides may provide the necessary protein makers for identifying in vivo virus-coded proteins.
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PMID:Comparison of the genomic organization of Kirsten and Harvey sarcoma viruses. 21 Dec 54

The genome of the defective avian tumor virus MH2 was identified as a RNA of 5.7 kilobases by its presence in different MH2-helper virus complexes and its absence from pure helper virus, by its unique fingerprint pattern of RNase T1-resistant (T1) oligonucleotides that differed from those of two helper virus RNAs, and by its structural analogy to the RNA of MC29, another avian acute leukemia virus. Two sets of sequences were distinguished in MH2 RNA: 66% hybridized with DNA complementary to helper-independent avian tumor viruses, termed group-specific, and 34% were specific. The percentage of specific sequences is considered a minimal estimate because the MH2 RNA used was about 30% contaminated by helper virus RNA. No sequences related to the transforming src gene of avian sarcoma viruses were found in MH2. MH2 shared three large T1 oligonucleotides with MC29, two of which could also be isolated from a RNase A- and T1-resistant hybrid formed between MH2 RNA and MC29 specific cDNA. These oligonucleotides belong to a group of six that define the specific segment of MC29 RNA described previously. The group-specific sequences of MH2 and MC29 RNA shared only the two smallest out of about 20 T1 oligonucleotides associated with MH2 RNA. It is concluded that the specific sequences of MH2 and MC29 are related, and it is proposed that they are necessary for, or identical with, the onc genes of these viruses. These sequences would define a related class of transforming genes in avian tumor viruses that differs from the src genes of avian sarcoma viruses.
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PMID:Avian acute leukemia viruses MC29 and MH2 share specific RNA sequences: evidence for a second class of transforming genes. 22

The effect of polyamines on ribonucleases in the presence of various inhibitors (poly(G), heparin, and rat liver RNase inhibitor) has been studied. Bovine pancreatic RNas A and a ribonuclease from horse submaxillary gland (RNase HS) were inhibited by the inhibitors, but RNase T1 and RNase M were not inhibited. Polyamines were found to restore the activites of RNase A and RNase HS inhibited by poly(G) or heparin but not those activities inhibited by rat liver RNase inhibitor. When poly(U) and poly(C) were used as substrates, the inhibitory effects of poly(G) and heparin were greater with poly(U) than poly(C) as a substrate. However, when poly(C) was used as a substrate in the presence of either of the above inhibitors, the restoration of RNase activity by sperimine was more efficient. In fact, a stimulatory effect was observed. From the double-reciprocal plots, it was concluded that polyamines restored the activiities of RNases by increasing the availability of the substrate and enzyme to each other. The restoration of enzyme activity by polyamines occurred through the binding of the polyamines to the inhibitor and the subsequent release of enzyme from the inhibitor.
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PMID:Studies on the restoration of the activities of Ribonucleases by polyamines in the presence of various ribonuclease inhibitors. 40 77


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