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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study describes the separation and purification of a reverse transciptiase from an orbital tumor of a patient with acute myelomonocytic leukemia. Specific reaction conditions with respect to ionic requirements and template-primers are reported. The purified enzyme was able to transcribe (rA)n . (dT)12, (rC)n . (dG)12, (OMeC)n . (dg)12 and the 70 S RNA from R(Mu)LV. Serological studies that the reverase transcriptase is antigenically related to reverse transcriptase from the type C woolly monkey virus-gibbon ape leukemia virus group.
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PMID:RNA-dependent DNA polymerase activity in ocular granulocytic sarcoma associated to acute myelomonocytic leukemia in Turkish children. Biochemical and immunological characterization of the enzyme. 615 28

Polyspermine-ribonuclease (Mr approximately 17 000) and the enzyme transcriptase from Rauscher-leukaemia virus (Mr approximately 70 000) form a complex Mr approx. 160 000) such that the molar ratio of polyspermine-ribonuclease to reverse transcriptase is 5:1. The most favourable condition for complex-formation is in a solution consisting of 0.01 M-Tris/HCl buffer, pH 7.5, 0.25 M-KCl and 1 mM-Mn2+ at 37 degrees C. The association of the two enzymes retains full RNAase activity, but reverse-transcriptase activity is completely inhibited when ribonuclease-sensitive polymers such as (dG)12 x (rC)n or viral 70S RNA are used as primer templates.
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PMID:Complexing reverse transcriptase with polyspermine-ribonuclease. 616 6

Reverse transcriptase from avian retrovirus has a physically associated DNA endonuclease with novel substrate and cofactor requirements. A similar endonuclease activity copurifies with pp32, a protein from viral cores that has been identified with the non-alpha region of the beta subunit of reverse transcriptase. Several temperature-sensitive mutants of avian retrovirus with thermolabile DNA polymerase were tested for thermal sensitivity of their DNA endonuclease activity. Two pol mutants of Rous sarcoma virus, ts335 and ts337, had thermolabile DNA endonuclease; a temperature-resistant revertant of ts335 had a heat-stable DNA endonuclease. DNA endonuclease is therefore a product of the pol gene and an integral part of the reverse transcriptase. A second class of pol mutants, typified by ts568 and ts553, had thermolabile DNA polymerase, but heat-stable DNA endonuclease.
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PMID:Virus-coded DNA endonuclease from avian retrovirus. 616 35

Reverse transcriptase from Rous sarcoma virus and avian myeloblastosis virus was purified by a rapid two-step procedure using chromatography on phosphocellulose and heparin-Sepharose. The resulting enzyme was homogeneous, had a high specific activity and was free of contaminating nucleases. This procedure has been adapted to small-scale preparation of enzyme from mutant virus containing thermolabile reverse transcriptase, and is equally suitable for large-scale enzyme purification.
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PMID:Purification of reverse transcriptase from avian retroviruses using affinity chromatography on heparin-sepharose. 616 44

Human oocytes in different stages of maturation were obtained by follicular aspiration from women given Clomovid and Gonadex. Particles similar to type-C virus were observed in three out of 16 oocytes. The particles were irregularly distributed along the oocyte membrane. They were seen both in a state of budding and lying free in the perivitelline space. Reverse transcriptase activity was detected in three out of nine samples of follicular fluid obtained from women other than those donating the oocytes. The supernatants from bat lung cells and dog thymus cells cultivated with oocytes or follicular fluids were tested for reverse transcriptase. An increased activity was observed only transiently in one case. It is assumed that these findings indicate the expression of endogenous retroviruses in human oocytes.
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PMID:Morphological and microbiological signs of endogenous C-virus in human oocytes. 617 30

Employing enzymatic reactions containing reverse transcriptase and appropriately defined substrates, we have demonstrated that the tRNATrp primer molecule required for the initiation of DNA synthesis is cleaved from viral DNA by an enzymatic activity associated with the reverse transcriptase molecule. Since the alpha subunit of reverse transcriptase facilitates release of the tRNATrp primer from viral DNA and this activity is inhibited by a known inhibitor of reverse-transcriptase-associated RNAase H, it appears that the RNAase H activity, rather than the DNA endonuclease activity, is involved in this reaction. The cleavage site for RNAase H-mediated removal of the tRNATrp primer from viral DNA is located at or near the tRNATrp-viral DNA junction, and transcription of most, if not all, of the tRNATrp-binding site into (+) polarity DNA occurs before RNAase-H-mediated cleavage takes place. These studies indicate that an additional function can be ascribed to the reverse-transcriptase-associated RNAase H activity, which in this instance acts like an endonuclease, not requiring the unblocked termini of an RNA-DNA hybrid molecule for its activity.
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PMID:Mechanism of release of the avian rotavirus tRNATrp primer molecule from viral DNA by ribonuclease H during reverse transcription. 618 6

Chromatography on heparin-Sepharose, known for its affinity for nucleotide-binding polypeptides, was used to purify the viral RNA-dependent DNA polymerase (reverse transcriptase) from the core polypeptides of simian foamy virus type 1. This procedure allowed the recovery of highly purified enzyme with a high specific activity. The average molecular weight of this monomeric enzyme is 81,000 and is thus comparable to that found for other known primate retroviruses. Reverse transcriptase activity of simian foamy virus type 1 requires a ribonucleotide template as a primer or otherwise a DNA with 3'-OH ends. Other optimal conditions of activity are reviewed. Heat inactivation studies led to the concept of an enzyme with two loci, one specific for the substrate and the other for the template-primer.
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PMID:Reverse transcriptase from simian foamy virus serotype 1: purification and characterization. 618 51

Particle-associated reverse transcriptase activity was detected in four human serum specimens and in two plasma-derived products, all of which had been shown to transmit non-A, non-B hepatitis (NANBH) to other human beings and/or chimpanzees. Reverse transcriptase activity was also detected in all twelve sera from patients with acute or chronic NANBH. In contrast, reverse transcriptase activity was found in only 2 of 49 serum specimens from healthy plasma donors and laboratory workers. Sucrose density gradient fractions of two of the infectious human sera (peak reverse transcriptase activity at 1.14 g/ml) transmitted NANBH to chimpanzees. Biochemical and enzymatic data indicate that the NANBH agent(s) is a retrovirus or is retrovirus-like.
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PMID:Detection of reverse transcriptase activity in association with the non-A, non-B hepatitis agent(s). 620 45

A temperature-sensitive coordinate mutant tsLA83 of Prague (PR-B) strain of Rous sarcoma virus at the nonpermissive temperature (41 degrees) produces noninfectious virus particles (NI-LA83) which contained only 3% of the reverse-transcriptase activity present in infectious virions. Analyses of [35S]methionine-labeled NI-LA83 showed the presence of all of the viral proteins except reverse transcriptase. Pulse-chase analyses of the virus-specified proteins in cells infected with LA83 or PR-B showed that the gag and glycoprotein precursors, Pr76gag and gPr95env, respectively, were processed at both 35 and 41 degrees. The reverse-transcriptase precursor, Pr180gag-pol, however, was not processed in LA83-infected cells at 41 degrees. In contrast, cells infected with LA83 or PR-B at 35 degrees as well as with PR-B at 41 degrees showed normal cleavage of Pr180gag-pol. A shiftdown of LA83-infected cells at 41 degrees to the permissive temperature 35 degrees resulted in the normal processing of Pr180gag-pol and production of infectious virus containing reverse transcriptase. Electron microscopic analysis showed that at 41 degrees cells infected with LA83 showed a large number of budding structures but fewer released particles. A shiftdown from 41 to 35 degrees resulted in an increase of virus particles with a concomitant decrease in budding structures suggesting that the processing of reverse-transcriptase precursor is related to virion assembly.
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PMID:Impaired cleavage of the joint gag-pol polyprotein precursor and virion assembly in a temperature-sensitive mutant of Rous sarcoma virus. 633 Sep 81

We have constructed recombinant DNA clones containing small complementary DNA (cDNA) sequences homologous to portions of a 4.8-kb yeast viral double-stranded RNA (dsRNA) (L1) that codes for the viral capsid polypeptide. Neither the viral dsRNA nor its in vitro transcript is polyadenylated; hence the cDNAs were synthesized by reverse transcriptase on the in vitro mRNA transcript made by the viral transcriptase, using sheared salmon sperm DNA as a random primer. This is the first reported cloning of cDNA homologous to a viral double-stranded RNA. This method should be of general utility for dsRNA viruses, since all have a capsid-associated transcriptase activity. The lengths of the overlapping cDNA inserts varied from 100 to 800 bp. About 40% of them mapped to the 5' end of the in vitro transcript, and these have been ordered. At least 1485 bp of this end of L1 is represented in the cloned cDNAs characterized. Using the cloned cDNAs as probes, we have shown that the L dsRNAs of two viral subtypes are similar at the transcription initiation site and dissimilar elsewhere.
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PMID:Cloning of cDNA to a yeast viral double-stranded RNA and comparison of three viral RNAs. 675 56


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