Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously demonstrated the presence of a reverse transcriptase-like enzyme in retroviral particles from patients with essential thrombocythemia, polycythemia vera, and chronic myelogenous leukemia. It was subsequently shown that the human genome contains 50 copies of HERV-K. HERV-K is a human endogenous class I retroviral element that contains gag, pol, and env open reading frames. Using both reverse transcriptase-polymerase chain reaction and ribonuclease protection assays, it is demonstrated that the HERV-K pol is expressed in human blood leukocytes. The data indicates that this expression is restricted in CML white cells and is the result of gene regulation.
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PMID:Expression of human endogenous retrovirus (HERV-K) in chronic myeloid leukemia. 750 41

HERV-K is a 50-copy, human endogenous, class 1 retroviral element that contains some polycistrons with gag, pol, and env open reading frames. Although expression of HERV-K proviruses has been shown in cultured human cell lines, expression of these elements has not been shown in human blood leukocytes. Using both reverse transcriptase-polymerase chain reaction and ribonuclease protection techniques, we show HERV-K pol gene expression in human blood leukocytes. Expression in blood leukocytes from 7 normal individuals was from a variety of different HERV-K proviruses, while restricted expression was observed in blood cells of 5 leukemia patients and 3 polycythemia vera patients. Evidence is presented suggesting that the restricted expression in leukemia blood cells is a result of gene regulation, not gene amplification.
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PMID:Expression of HERV-K proviruses in human leukocytes. 768 17

P40 is encoded by the first open reading frame of the human LINE-1 retrotransposon and is found in a large cytoplasmic ribonucleoprotein (RNP) complex, the p40 RNP-complex, in association with LINE-1 RNA(s) in human teratocarcinoma cell lines. We report here investigations on the stability of the p40 RNP-complex against various nucleases and high salt (0.5 M NaCl) treatment. The results indicate that (1) the p40 RNP-complex is dissociated after ribonuclease or high salt treatment, (2) DNase I does not disrupt the complex, (3) after dissociation of the complex, p40 maintain protein-protein interactions but in smaller complexes, and (4) p40 is not associated with the LINE-1 RNA(s) after high salt treatment. These observations suggest that the RNA molecule(s) is(are) essential for the stability of the large p40 complex and that the complex has a structure which allows various nucleases to reach the RNA. These features are distinct from those of typical virus and virus-like particles of retroviruses and other retrotransposons, respectively. Together with the fact that no significant sequence homology exists between p40 and the gag and gag-like proteins, it is likely that the p40 RNP-complex is structurally different from the typical virus and virus-like particles.
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PMID:Ribonuclease and high salt sensitivity of the ribonucleoprotein complex formed by the human LINE-1 retrotransposon. 930 51

An HIV-1-based expression vector has been constructed that produces protective genes tightly regulated by HIV-1 Tat and Rev proteins. The vector contains either a single protective gene (HIV-1 gag dominant negative mutant (delta-gag)) or a combination of two different protective genes (delta-gag and eosinophil-derived neurotoxin (EDN), a human ribonuclease) which are expressed from a dicistronic mRNA. After stable transfection of CEM T cells and following challenge with HIV-1, viral production was completely inhibited in cells transduced with the vector producing both delta-gag and EDN and delayed in cells producing delta-gag alone. In addition, cotransfection of HeLa-Tat cells with an infectious HIV-1 molecular clone and either protective vector demonstrated that the HIV-1 packaging signals present in the constructs were functional and allowed the efficient assembly of the protective RNAs into HIV-1 virions, thus potentially transmitting protection to the HIV-1 target cells.
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PMID:Inhibition of HIV-1 replication by combined expression of gag dominant negative mutant and a human ribonuclease in a tightly controlled HIV-1 inducible vector. 953 66

We have used a ribonuclease protection assay to investigate RNase H cleavage of HIV-1 mRNA mediated by phosphorothioate antisense oligonucleotides complementary to the gag region of the HIV-1 genome in vitro. Cell lysate experiments in H9 and U937 cells chronically infected with HIV-1 IIIB showed RNase H cleavage of unspliced gag message but no cleavage of spliced message which did not contain the target gag region. RNase H cleavage products were detected at oligonucleotide concentrations as low as 0.01 microM and the RNase H activity was seen to be concentration dependent. Similar experiments with 1-, 3- and 5-mismatch oligonucleotides demonstrated sequence specificity at low concentrations, with cleavage of gag mRNA correlating with the predicted activities of the parent and mismatch oligonucleotides based on their hybridization melting temperatures. Experiments in living cells suggested that RNase H-specific antisense activity was largely determined by the amount of oligonucleotide taken up by the different cell lines studied. RNase H cleavage products were detected in antisense oligonucleotide treated MT-4 cells acutely infected with HIV-1 IIIB, but not in infected H9 cells treated with oligonucleotide under the same conditions. The data presented demonstrate potent and specific RNase H cleavage of HIV-1 mRNA mediated by an antisense oligonucleotide targeted to HIV-1 gag mRNA, and are in agreement with previous reports that the major obstacle to demonstrating antisense activity in living cells remains the lack of penetration of these agents into the desired cellular compartment.
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PMID:Sequence-specific RNase H cleavage of gag mRNA from HIV-1 infected cells by an antisense oligonucleotide in vitro. 983 98

We introduce a new simple methodology allowing the measurement of (1)H-(15)N residual dipolar couplings, dipolar shifts, and unpaired electron-amide proton distances. This method utilizes a zinc finger tag fused at either the N- or the C-terminus of a protein. We have demonstrated this fusion strategy by incorporating the zinc finger of the retroviral gag protein onto the C-terminus of barnase, a ribonuclease produced by Bacillus amiloliquifaciance. We show that this tag can be substituted with cobalt and manganese. Binding of cobalt to the gag zinc finger-barnase fusion protein introduced sufficient anisotropic paramagnetic susceptibility for orientation of the molecule in the magnetic field. Partial alignment permitted measurement of (1)J(HN) scalar couplings along with dipolar couplings. Replacement of bound cobalt with diamagnetic zinc removes the paramagnetic-induced orientation of barnase, permitting the measurement of only (1)J(HN) scalar couplings. Dipolar couplings, ranging from -0.9 to 0.6 Hz, were easily measured from the difference in splitting frequencies in the presence of cobalt and zinc. The observed paramagnetic anisotropy induced by cobalt binding to the metal binding tag also permitted measurement of dipolar shifts. Substitution of manganese into the metal binding tag permitted the measurement of unpaired electron-amide proton distances using paramagnetic relaxation enhancement methodology. The availability of both amide proton dipolar shifts and unpaired electron to amide proton distances permitted the direct calculation of z-coordinates for individual amide protons. This approach is robust and will prove powerful for global fold determination of proteins identified in genome initiatives.
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PMID:Calculation of z-coordinates and orientational restraints using a metal binding tag. 1110 1