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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of direct virus infection as a determining factor in acquired immunodeficiency syndrome (AIDS) dementia was investigated using in situ hybridisation for human immunodeficiency virus (HIV) and human cytomegalovirus (HCMV). Four of the five AIDS dementia patients in this series demonstrated HIV infected cells distributed in widely different parts of the brain, but only one case showed HCMV infected cells. The greater abundance of HIV was in subcortical white matter in nodular areas consisting of monocyte/macrophage infiltrates. The cells were occasionally arranged as a multinucleated syncitium. In two cases, a few large cells with the appearance of neurons were positive for HIV hybridisation. By appropriate treatment with ribonuclease, it was shown that hybridisation was primarily to HIV RNA. HCMV infected cells were observed in small numbers in only one of the positive cases, suggesting that HCMV is not a determining factor in AIDS dementia. HCMV positive cells were located in the grey matter, with an appearance suggestive of neurons. Cells expressing the MHC-class II antigen HLA-DR, a marker of reactive microglia and macrophages, were observed to be extensive in affected brain sections in the one case examined. These cells were present in greater number than HIV infected cells. In this case, extensive numbers of HIV infected cells were noticed along the peripheral margin of the substantia innominata. This could indicate infection in this case of a critical brain region from the cerebrospinal fluid.
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PMID:Examination of brains of AIDS cases for human immunodeficiency virus and human cytomegalovirus nucleic acids. 254 95

High molecular weight DNA of up to 20 kbp and, additionally, an RNase-insensitive RNA of more than 60 b were isolated from plasmapheresis fluids taken from patients with active systemic lupus erythematosus (SLE). Similar nucleic acids could not be demonstrated in the plasma samples from patients with Waldenstroem's disease, rheumatoid arthritis, myasthenia gravis, and other diseases including active systemic disorders. The purified nucleic acids were analyzed in several ways; they proved to be immunogenic by inducing polyclonal and monoclonal antibodies to natural DNA as well as to synthetic polynucleotides (e.g. polyguanylic acid) after injection into experimental animals (rabbits or mice respectively). Biochemical and molecular cloning analysis of the DNA revealed features like high levels of CpG-dinucleotides, usually not observed in common human DNA. A possible exogenous origin was substantiated by comparative sequence studies of cloned plasma DNA, which showed homologies to human retroviruses, e.g. PL1 (85%/60 b) and the sequences of the gag and pol genes of human immunodeficiency virus type I (85%/157 b). Experiments applying isolated plasma nucleic acids in transfection experiments showed the induction of morphological changes in an EBV-immortalized B-cell line drawn from a healthy human donor, such as vacuolization and syncitia formation. Northern blot analysis demonstrated, exclusively in the transfected cell line, the expression of mRNA homologous to the cloned plasma DNA. Using this clone as a probe, homologous sequences could be demonstrated by Northern blot analysis in EBV-immortalized cell lines from SLE patients only and, by means of DNA amplification, in peripheral blood lymphocytes from SLE and AIDS patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Are retroviruses involved in the pathogenesis of SLE? Evidence demonstrated by molecular analysis of nucleic acids from SLE patients' plasma. 269 25

The genome of human immunodeficiency virus encodes a protein that dramatically elevates amounts of viral proteins. The precise mechanism of this trans-activation remains to be established. It has been reported that trans-activation can occur without major changes in the levels of mRNA. We constructed recombinant plasmids containing those viral sequences required in cis for trans-activation linked to the chloramphenicol acetyltransferase gene. These plasmids were introduced into cultured cells in either the presence or absence of a second plasmid that directed expression of the viral trans-activator protein. Expression of the chloramphenicol acetyltransferase gene was measured at the level of protein (by enzymatic assay) and RNA (by ribonuclease protection and primer extension). Our results demonstrate that trans-activation is accompanied by large increases in mRNA levels; these increases may be sufficient to explain the elevated levels of trans-activated protein.
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PMID:Elevated levels of mRNA can account for the trans-activation of human immunodeficiency virus. 302 48

A homology has been found between an octapeptide involved in attachment of the human immunodeficiency virus to helper/inducer T cells and an octapeptide segment of bovine pancreatic ribonuclease A. This segment (residues 19-26) contains the sites for subtilisin cleavage of this enzyme into the S-peptide and S-protein. From the X-ray crystal structure of ribonuclease, this sequence is known to be exposed to solvent and interacts little with the rest of the protein. A structure for the human immunodeficiency virus attachment peptide can be deduced from this homology, as a well-defined structure has been determined for this sequence in ribonuclease. This can be readily accomplished using previously developed computer methods based upon conformational energy calculations. The calculated structure for human immunodeficiency virus peptide is identical to the ribonuclease segment (19-26) in backbone conformation. It is stabilized by internal interactions of nonpolar residues, and by exposure of polar hydroxyl groups. The results suggest that the T-cell human immunodeficiency virus receptor may be hydrophilic in nature and that conservation of the sequence in two presumably functionally unrelated proteins is related to the need for conservation of exposed structure.
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PMID:A strong homology exists between the active T-cell binding gp120 octapeptide of human immunodeficiency virus and the subtilisin cleavage peptide of bovine ribonuclease A. 303 Mar 17

After infection of the respective target cells with the human immunodeficiency virus (HIV-1) viral progeny is produced only after a short temporary delay of some days, depending on cell type. After this period of time a sudden onset of HIV-1 protein synthesis with a dramatic increase in virus release occurs. (2'-5')Oligoriboadenylates [(2'-5')A], capable to activate a latent ribonuclease (RNase L) degrading both mRNA and rRNA, are known mediators involved in the early response of cells to virus infection. Here we show that the (2'-5')A-synthesizing (2'-5')A synthetase, which is inducible by interferon and activated by double-stranded RNA, as well as a (2'-5')A nuclease (2',3'-exoribonuclease) are associated with the nuclear matrix of uninfected and infected H9 cells, also in the absence of interferon. Infection of H9 cells with HIV-1 was found to cause a strong (7.7-fold) enhancement of (2'-5')A synthetase activity and a smaller (2-fold) increase of 2',3'-exoribonuclease activity. Simultaneously the concentration of synthesized (2'-5')A increased 5 to 10 times in isolated nuclei. After incubation for 2 to 3 days both enzyme activities reached a maximum and then dropped below their initial values. Concomitantly a drastic increase in virus production occurred, as judged by reverse transcriptase activity in the culture fluid. These results suggest that the (nuclear matrix-associated) (2'-5')A system might be important during the initial stage of HIV infection, also by destructing matrix-bound viral messengers.
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PMID:Alteration of nuclear (2'-5')oligoriboadenylate synthetase and nuclease activities preceding replication of human immunodeficiency virus in H9 cells. 322 94

Three human cell lines of astrocytic origin were evaluated for expression of a human T-lymphocyte surface glycoprotein, T4, which also serves as a cellular receptor for the human immunodeficiency virus (AIDS virus, HIV). T4 antigen was detected on the cell surface of 2 of these cell lines using monoclonal OKT-4 antibody and flow cytometry. Gene transcripts encoding the T4 molecule were detected by a ribonuclease protection assay in surface T4-positive and -negative cells. Our results suggest that astrocytes may serve as targets for HIV infection in the brain.
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PMID:Expression of the T4 molecule (AIDS virus receptor) by human brain-derived cells. 349 19

Capillary electrophoresis with laser-induced fluorescent detection, a one-dimensional version of the well-established planar analytical method of polyacrylamide gel electrophoresis, has been proven to be a powerful new microanalytical method for profiling complex carbohydrates. In this paper a comparison is presented between the planar high concentration polyacrylamide gel electrophoresis method and capillary electrophoresis of different carbohydrates with respect to performance and efficiency. N-Linked oligosaccharides were released from several glycoproteins, including fetuin, human immunodeficiency virus (HIV) envelope recombinant glycoprotein (GP-120), alpha 1-acid glycoprotein and ribonuclease B, using recombinant peptide-N-glycosidase F (PNGase F). Both separation methods involve labeling of the released carbohydrates at the reducing end with the fluorescent dye, disodium 8-amino-1,3,6-naphthalene trisulfonate (ANTS). Fluorophore labeling was followed by separation of the labeled oligosaccharides either by high concentration polyacrylamide gel electrophoresis or capillary electrophoresis.
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PMID:Capillary and slab gel electrophoresis profiling of oligosaccharides. 749 47

In the presence of Mn2+, reverse transcriptase of both human immunodeficiency virus and murine leukemia virus hydrolyzes duplex RNA. However, designating this novel activity RNase D conflicts with Escherichia coli RNase D, which participates in tRNA processing. On the basis of its location in the RNase H domain, we propose that this novel retroviral activity be redesignated RNase H*.
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PMID:Redesignation of the RNase D activity associated with retroviral reverse transcriptase as RNase H. 750 4

Cleavage specificity of RNase HI was examined on model Okazaki fragments, to determine the likely role of this nuclease in lagging strand DNA replication. Each substrate was prepared by annealing a short RNA primer, made by transcription in vitro, to a single-stranded synthetic DNA template, and subsequently extending the primer by DNA polymerization. The calf thymus RNase HI makes a structure-specific endonucleolytic cleavage in the RNA primer, releasing it intact, and leaving a mono-ribonucleotide at the 5' terminus of the RNA-DNA junction. This specific cleavage, one nucleotide upstream of the RNA-DNA junction, is RNA primer sequence- and length-independent. Cleavage specificity is lost if the RNA primer is not extended with DNA, or if the substrate has a nick at the RNA-DNA junction. In addition, the cleavage at a single site requires Mg2+. Cleavage in the presence of Mn2+ is less specific. Neither human immunodeficiency virus reverse transcriptase nor Escherichia coli RNases H perform such a structure-specific cleavage before an RNA-DNA junction. Our work indicates that calf RNase HI is designed to recognize Okazaki fragments. It has the specificity to remove their initiator RNA segments, except for one ribonucleotide, by a single endonucleolytic cleavage in vivo.
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PMID:Structure-specific cleavage of the RNA primer from Okazaki fragments by calf thymus RNase HI. 752 96

When designed to cleave a target RNA in trans, the hammerhead ribozyme contains two antisense flanks which form helix I and helix III by pairing with the complementary target RNA. The sequences forming helix II are contained on the ribozyme strand and represent a major structural component of the hammerhead structure. In the case of an inhibitory 429 nucleotides long trans-ribozyme (2as-Rz12) which was directed against the 5'-leader/gag region of the human immunodeficiency virus type 1 (HIV-1), helix II was not pre-formed in the single-stranded molecule. Thus, major structural changes are necessary before cleavage can occur. To study whether pre-formation of helix II in the non-paired 2as-Rz12 RNA could influence the observed cleavage rate in vitro and its inhibitory activity on HIV-1 replication, we extended the 4 base pair helix II of 2as-Rz12 to 6, 10, 21, and 22 base pairs respectively. Limited RNase cleavage reactions performed in vitro at 37 degrees C and at physiological ion strength indicated that a helix II of the hammerhead domain was pre-formed when its length was at least six base pairs. This modification neither affected the association rate with target RNA nor the cleavage rate in vitro. In contrast to this, extension of helix II led to a significantly decreased inhibition of HIV-1 replication in human cells. Together with the finding of others that shortening of helix II to less than two base pairs reduces the catalytic activity in vitro, this observation indicates that the length of helix II in the naturally occurring RNAs with a hammerhead domain is already close or identical to the optimal length for catalytic activity in vitro and in vivo.
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PMID:Extension of helix II of an HIV-1-directed hammerhead ribozyme with long antisense flanks does not alter kinetic parameters in vitro but causes loss of the inhibitory potential in living cells. 752 30


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