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

---

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

The human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT) is a protein of 66 kDa, p66, which contains two domains, an amino-terminal DNA polymerase and an RNase H at the carboxy terminus of the molecule. In order to characterize the mode of action of the RNase H, two previously described mutant enzymes were used, with substitutions in the highly conserved histidine 539, which was mutated to the neutral amino acid asparagine and to the negatively charged aspartate. The purified wild-type (wt) and mutant (mt) enzyme activities are analyzed here using RNA-DNA hybrids consisting of in vitro transcribed RNA that harbors the polypurine tract (PPT) from HIV-1 and DNA oligonucleotides complementary to the PPT or to other regions of the RNA. Analysis of the radioactively labeled RNA of these model hybrids after RNase H treatment indicates that both, wt and mt enzymes, are capable of cleaving the RNA in an endonucleolytic manner. The mt enzymes exhibit a severely reduced exonuclease activity. They are more sensitive towards salt and competition with excess of unlabeled hybrid, suggesting a reduced substrate binding affinity. DNA elongation by the RT is coupled with RNA hydrolysis by the 3'-5' exonuclease of the wt RNase H. The RNase Hmt of the mt enzymes, however, does not exhibit such processive 3'-5' exonuclease activity during DNA synthesis but gives rise to sporadic endonucleolytic cuts, whereas the RT is not affected. The endonuclease activities of the RNase H mt enzymes exhibit cleavage preferences in the absence or presence of DNA synthesis different from those of the wt enzyme. They cannot recognize specific sequences required to generate a PPT-primer and therefore cannot initiate plus-strand DNA synthesis in vitro at the 3' end of the PPT, which is essential for viral replication.
...
PMID:Mutations of a conserved residue within HIV-1 ribonuclease H affect its exo- and endonuclease activities. 171 5

The exonucleolytic activities associated with herpes simplex virus type-1 (HSV-1) DNA polymerase and DNase were compared. The unique properties of these nucleases were assessed by applying biochemical and immunological methods as well as by genetics. In contrast to the viral DNA polymerase, HSV DNase is equipped with a 5'-3'-exonuclease activity. Under reaction conditions optimal for HSV DNA polymerase, i.e. at high ionic strength, HSV DNase exhibited only limited endonucleolytic activity and degraded double-stranded DNA in a very processive manner and exclusively in the 5'-3' direction, producing predominantly mononucleotides. Both viral enzymes displayed significant RNase activity which could be correlated with the endogenous endonucleolytic and 5'-3'-exonucleolytic activities of the DNase and the polymerase-associated 3'-5' exonuclease. The tight linkage of polymerizing and exonucleolytic functions of the viral DNA polymerase was demonstrated by their identical response to (a) thermal inactivation, (b) drug inhibition and (c) neutralization by polyclonal antibodies reacting specifically with the N-terminal, central and C-terminal polypeptide domains of HSV-1 DNA polymerase. From the data presented it can be concluded that the cryptic 3'-5' exonuclease is the only exonucleolytic activity associated with the viral DNA polymerase.
...
PMID:Comparison of exonucleolytic activities of herpes simplex virus type-1 DNA polymerase and DNase. 216 60

A cell-free system that catalyzes DNA replication was prepared from cytoplasmic extracts of Vero cells infected with African swine fever virus (ASFV). The cells were permeabilized with lysolecithin and disrupted by mild mechanical action and the nuclei were removed by low-speed centrifugation. Extracts prepared from infected cells at the time of maximal DNA replication incorporated [alpha-32P]dTTP into acid-insoluble material that was sensitive to DNase and resistant to RNase. The reaction was inhibited by phosphonoacetic acid, an inhibitor of ASFV-specific DNA polymerase. Extracts from mock-infected cells had a negligible activity. Micrococcal nuclease-treated extracts were able to replicate added virion DNA or viral replicative DNA. An increase in the mass of DNA detected by ethidium bromide staining and by dot blot hybridization with ASFV DNA showed that the incorporation was due to true replication. Plasmid DNA was also replicated, which indicates that ASFV-specific DNA polymerase does not require a virus-specific origin of replication. The pattern of fragments generated by EcoRI digestion of the in vitro product was characteristic of viral replicative DNA. Hybridization with a recombinant plasmid containing a terminal fragment of ASFV DNA confirmed the presence of dimer terminal ASFV fragments presumably generated from concatemeric replicative intermediates.
...
PMID:In vitro DNA replication by cytoplasmic extracts from cells infected with African swine fever virus. 221 42

Biochemical and morphological evidence indicates that a type-C retrovirus is present in the blood of swine (both leukemic and nonleukemic) exposed to strontium-90 radiation. Nonexposed swine that were leukemic also had virus present. The virus was shown to contain an RNase-sensitive DNA polymerase activity with cation, detergent and template requirements similar to those of known viral reverse transcriptases. The buoyant density of the virus was 1.14 to 1.16 g/ml, which can be converted, by treatment with ether, to a virion core having a density of 1.20 to 1.23 g/ml. Linear regression analysis indicated a correlation between virus-associated DNA polymerase activity and the number of blast cells in the peripheral blood.
...
PMID:Evidence for retrovirus in miniature swine with radiation-induced leukemia or metaplasia. 257 82

A highly selective affinity labeling procedure has been applied to map the active center of DNA primase from the yeast Saccharomyces cerevisiae. Enzyme molecules that have been modified by covalent attachment of benzaldehyde derivatives of adenine nucleotides are autocatalytically labeled by incubation with a radioactive ribonucleoside triphosphate. The affinity labeling of primase requires a template DNA, is not affected by DNase and RNase treatments, but is sensitive to proteinase K. Both the p58 and p48 subunits of yeast DNA primase appear to participate in the formation of the catalytic site of the enzyme, although UV-photocross-linking with [alpha-32P]ATP locates the ribonucleoside triphosphate binding site exclusively on the p48 polypeptide. The fixation of the radioactive product has been carried out also after the enzymatic reaction. Under this condition the RNA primers synthesized by the DNA polymerase-primase complex under uncoupled DNA synthesis conditions are linked to both DNA primase and DNA polymerase. When DNA synthesis is allowed to proceed first, the labeled RNA chains are fixed exclusively to the DNA polymerase polypeptide. These results, in accord with previous data, have been used to propose a model illustrating the interactions and the putative roles of the polypeptides of the DNA polymerase-primase complex.
...
PMID:Affinity labeling of the active center and ribonucleoside triphosphate binding site of yeast DNA primase. 264 56

A tumor-derived factor that inhibits cellular DNA synthesis was identified. The factor was extractable from a small-cell lung carcinoma cell line grown in either chemically defined medium or nu/nu mice and inhibited tritiated thymidine ([3H]dThd) incorporation by tumor cell lines of autologous, allogeneic, and xenogeneic origins. The viability of nonproliferating cells from normal tissue was not affected. Tumor extract inhibitory activity was trypsin labile but was resistant to other proteases, neuraminidase, lipase, DNase, RNase, glucosidase, extremes of pH-temperature, and reducing conditions. Inhibitory activity was reversibly bound to helix pomatia lectin but not to lentil, wheat germ, or concanavalin A lectins. Purification by size-exclusion high-performance liquid chromatography yielded a bioactive unimodal 12-kilodalton (kd) peak. The bioactive 12-kd moiety could be eluted from sodium dodecyl sulfate-polyacrylamide gels. Redosing of populations of the T-lymphoblastoid cell line CEM achieved an early (24 hr) sustained depression of pulse [3H]dThd incorporation and ultimately led to decreased population density of factor-treated populations. DNA histogram analysis demonstrated no change in cell cycle phase distribution after factor treatment. 5-Bromo-2'-deoxyuridine (BrdUrd) vs. propidium iodide with the two-parameter Fluorescence-Activated Cell Sorter analysis showed relative inhibition of non-S-phase BrdUrd uptake at 24 hours. A cell-free DNA polymerase assay demonstrated significant inhibition of non-alpha-polymerase-associated DNA synthesis in factor-treated cells. These studies suggest that this tumor-derived inhibitor of DNA synthesis represents a class of cellular products involved in the autoregulation of growth by regulation of DNA synthetic activity.
...
PMID:Inhibition of DNA synthesis by a small-cell lung carcinoma-derived protein. 302 Mar 1

To date the only point mutations demonstrated to cause hemophilia are C to T transitions in TaqI sites. These were detected by screening Southern blots with cloned factor VIII probes. During the development of improved methods for detecting and analyzing mutations in genomic DNA, a novel G to C transversion mutation has been identified. This rare transversion results in a missense mutation, with proline being substituted for arginine in one of the active domains of the factor VIII molecule. The results suggest that the improved methods will be useful for detecting mutations in hemophilia as well as in other genetic disorders. In this method, specific DNA sequences in genomic DNA are amplified using oligonucleotide primers and a heat-resistant DNA polymerase. Mutations are detected and localized in the amplified samples by RNase A cleavage, and the altered region is then sequenced.
...
PMID:A novel missense mutation in the factor VIII gene identified by analysis of amplified hemophilia DNA sequences. 312 81

Maedi virus contains a ribonucleic acid (RNA) which can be resolved into three major components, namely, 62S, 33S, and 13S, by sucrose gradient centrifugation. The presence of RNA- and deoxyribonucleic acid (DNA)-dependent DNA polymerase in virions of maedi virus was demonstrated. The enzyme product could be converted into acid-soluble form by pancreatic deoxyribonuclease, but was resistant to digestion by pancreatic ribonuclease and to hydrolysis by NaOH.
...
PMID:Properties of maedi nucleic acid and the presence of ribonucleic acid- and deoxyribonucleic acid-dependent deoxyribonucleic acid polymerase in the virions. 411 44

An RNA-directed DNA polymerase was isolated from the peripheral blood leukocytes of a patient with acute myelomonocytic leukemia by successive purification of a particulate cytoplasmic fraction with endogenous, ribonuclease-sensitive DNA polymerase activity. Like RNA-directed DNA polymerase from mammalian type-C virus, the human leukemic cell enzyme efficiently utilized (A)(n).(dT)(12-18) and (C)(n).(dG)(12-18) and had an approximate molecular weight of 70,000. Further, the leukemic cell enzyme was strongly inhibited by antisera to RNA-directed DNA polymerase of primate type-C virus in a fashion similar to that noted with an extensively purified RNA-directed DNA polymerase from a person with acute myelogenous leukemia [Todaro, G.J. & Gallo, R.C. (1973), Nature 244, 206]. By these biochemical and immunological results the leukemic cell enzyme could be differentiated from all other known cellular DNA polymerases but could not be distinguished from RNA-directed DNA polymerase of primate type-C virus. We interpret these data, combined with observations published elsewhere, to indicate that human acute myelogenous leukemia cells contain components related to primate type-C virus. The parameters used in this study may provide the specificity and sensitivity required for determining the presence or absence and (if present) the relatedness of RNA-directed DNA polymerase in other cases and types of human leukemia.
...
PMID:Relationship between RNA-directed DNA polymerase (reverse transcriptase) from human acute leukemic blood cells and primate type-C viruses. 413 50

A highly active and stable DNA polymerase was found in purified preparations of two murine sarcoma viruses. Enzyme activity is not detected in most virus preparations unless they are treated with low concentrations of a nonionic detergent such as Nonidet P-40. The incorporation of labeled thymidine triphosphate requires all four deoxyribonucleoside triphosphates and either Mg(2+) or Mn(2+). Enzyme activity is proportional to virus concentration and is linear with time up to 90 min. That the template is RNA is suggested by the reduction in polymerase activity upon treatment of murine sarcoma virus with RNase, and by the absence of detectable amounts of DNA in the virus. That the product is DNA is shown by the incorporation of all four deoxyribo-nucleoside triphosphates into an acid-insoluble product which is stable in alkali, is destroyed by DNase, sediments in alkaline sucrose gradients with a sedimentation coefficient of 7 S, and bands in isopycnic CsCl gradients with a mean buoyant density of 1.700.
...
PMID:Mechanism of carcinogenesis by RNA tumor viruses. I. An RNA-dependent DNA polymerase in murine sarcoma viruses. 431 86


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---