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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immunoprecipitation of labeled extracts from murine leukemia virus-infected cells with antisera specific for internal structural (gag) proteins yields three major gag-related polyproteins with molecular weights of 180,000 (Pr180gag-pol), 80,000, and 65,000 (Pr65gag). It has been shown by others that Pr65gag is the immediate precursor of the internal structural (gag) protein, and that Pr180gag-pol is the precursor to reverse transcriptase. In studies reported here, the 80,000-dalton gag-related polyprotein from Moloney strain murine leukemia virus (M-MuLV)-infected cells was found to be glycosylated by the following criteria: (i) incorporation of [3H]mannose, (ii) a change in electrophoretic mobility upon digestion with endoglycosidase H, and (iii) a change in electrophoretic mobility when glycosylation was inhibited by treatment of the cells with tunicamycin during labeling. The 80,000-dalton gag polyprotein has therefore been designated GpP80gag. The unglycosylated form of GpP80gag was a polypeptide of 75,000 daltons. A comparison of [3H]mannose and [3H]galactose labeling experiments suggested that GpP80gag is further glycosylated to yield a glycopolypeptide of 95,000 daltons. This 95,000-dalton polypeptide is relatively rapidly cleaved to yield two glycopeptides of 55,000 and 40,000 daltons which are released into the cell culture fluid, as soluble proteins. Cell-free translation of M-MuLV genomic RNA resulted in two major gag-related products of 75,000 and 65,000 daltons. The 65,000-dalton gag-related cell-free translation product comigrated with Pr65gag, and the 75,000-dalton cell-free product comigrated with the unglycosylated form of GpP80gag. Both of the gag-related cell-free translation products could be labeled with [35S]formyl methionine, which is incorporated only as the N-terminal amino acid during translation. Other investigators have shown that GpP80gag and Pr65gag differ at their N-termini, and these results combined with those reported here suggest that GpP80gag and Pr65gag are translated from two separate initiation sites in M-MuLV RNA.
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PMID:gag-Related polyproteins of Moloney murine leukemia virus: evidence for independent synthesis of glycosylated and unglycosylated forms. 46 93

[3H]tyrosine-labeled viral precursor polyproteins and known mature viral proteins derived from the Rauscher murine leukemia virus gag and pol genes were examined by two-dimensional tryptic peptide mapping. Pr200gag-pol was found to contain peptide sequences of the viral core proteins p30, p15, p12, and p10, as well as peptide sequences found in the cell-associated reverse transcriptase. Intermediate reverse transcriptase precursor Pr125pol lacked peptide sequences of the four-core proteins but contained reverse transcriptase-specific tryptic peptides plus two additional tyrosine-containing tryptic peptides not related to gag or pol gene products. Methionine-containing tryptic peptide analysis also suggested the presence of additional protein material in Pr125pol (Kopchick et al., Proc. Natl. Acad. Sci. U.S.A. 75:2016-2020, 1978). Pr200gag-pol, although containing both viral core and reverse transcriptase-assoicated methionine and tyrosine tryptic peptides, also contained additional tryptic peptides. Thes are of two classes: (i) tryptic peptides associated with the Pr125pol but not Pr80pol and (ii) tryptic peptides not found in Pr125pol or in any known viral protein. One interpretation of these results is that Pr200gag-pol contains additional gene products aside from the gag and pol genes. Pr80gag and Pr65gag peptide maps were also examined and found to have sequences of all four core proteins. Pr65gag was found to contain two p30 tyrosine tryptic peptides that were absent in Pr80gag, suggesting that Pr80gag may not be the precursor to Pr65gag. Pr80gag, as expected from its larger size, also contained tryptic peptides not found in Pr65gag. Two of these additional Pr80gag tryptic peptides were found in Pr80pol as well but not in any of the viral core proteins, suggesting that Pr80gag and Pr80pol may have overlapping peptide sequences. Consistent with this finding is the conclusion that Pr80gag terminates within the pol gene. A model that describes the relationship of these recent findings to viral gene products is presented.
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PMID:Tryptic peptide analysis of gag and gag-pol gene products of Rauscher murine leukemia virus. 46 95

Translation of Rauscher murine leukemia virus (R-MuLV) 35S RNA in an mRNA-dependent cell-free protein-synthesizing system yields polypeptides identical to authentic Pr65gag, the R-MuLV gag precursor, and Pr200gag-pol, the precursor to the R-MuLV reverse transcriptase. In addition to these polypeptides, the cell-free product contains a family of polypeptides of less than 65,000 molecular weight which appear to be generated by premature termination of protein synthesis within the viral gag gene. We compared the tryptic maps of several of these less than 65,000-molecular-weight premature termination polypeptides with that of full-size Pr65gag and found a progressive loss of tryptic peptides which could be assigned to known R-MuLV gag proteins. A 40,000-molecular-weight fragment, P40gag, lacked p10 and part of p30, placing p10 at the C terminus pf Pr65gag and p30 ajacent to it. Fragments of 33,000 (P33gag) and 27,000 to 28,000 (P27/28gag) molecular weight showed a successive loss of additional p30 tryptic peptides, but no loss of either p15 or p12. An 18,000-molecular-weight fragment lost p12 but retained p15. These data suggest an R-MuLV gag gene order of NH2-p15-p12-p30-p10-COOH.
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PMID:Tryptic peptide analyses of polypeptides generated by premature termination of cell-free protein synthesis allow a determination of the Rauscher leukemia virus gag gene order. 73 99

The use of exclusionary techniques in the procurement of donors for bone allografts greatly reduces chances for disease transmission. Furthermore, treatment of HIV with either chemical agents or strong acids will effectively inactivate the AIDS virus. These data are taken as indirect proof that the risk of obtaining AIDS from a freeze-dried bone allograft is highly remote. The purpose of this study is to obtain direct evidence that the processing of a demineralized freeze-dried bone allograft would render the allograft safe for human use. In Part I, human cortical bone was obtained from a cadaveric source and tested to be free of HIV contamination. The bone was spiked with 5.26 x 10(9) viral particles. This corresponded to 148 micrograms of total viral protein. In Part II, cortical bone was procured from a donor who died of AIDS. In both Parts I and II, the cortical bone was ground to yield particle sizes of 90 to 500 microns. Test samples were treated with a virucidal agent and demineralized in HCl. Control samples were left untreated. All samples were cocultivated with stimulated peripheral blood lymphocytes and assayed for p24 core protein, reverse transcriptase, and viral gag gene by polymerase chain reaction (PCR). In Part I, the HIV spiking experiment, untreated virus infected particulate bone was positive for HIV replication. Treated samples were negative when assayed for HIV. Bone samples in Part II, HIV infected bone, were positive by PCR. Replication of viable HIV could not be demonstrated after treatment. It was concluded that demineralization and treatment with a virucidal agent inactivates HIV in spiked and infected bone.
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PMID:HIV inactivation in a bone allograft. 128 53

Drosophila retrotransposon copia produces virus-like particles (VLPs) in the nuclei of cultured Drosophila cells. The VLPs contain copia RNA and reverse transcriptase activity, and thus, play a major role in copia replication. Here we have expressed the copia gag polyprotein precursor in yeast. The precursor, which includes copia protease itself, showed correct autoprocessing to produce a unique multi-lamella structure in the nuclei of the yeast cells. This expression system should be useful for the analysis of nuclear localization of the major copia VLP protein, and furthermore, would provide important information concerning the mechanism of copia VLPs formation.
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PMID:Production of a unique multi-lamella structure in the nuclei of yeast expressing Drosophila copia gag precursor. 131 48

An interspersed sequence has been isolated from the genome of D. silvestris, a species endemic to the Hawaiian Islands. The LOA element is 7.7 kb long and its 3' end consists of (TAA)n tandem repeats. Five different LOA elements were isolated, of which three were truncated at their 5' ends. Large deletions within the elements were frequent. A consensus sequence of the LOA element has been constructed using the nucleotide sequence of three elements. Two overlapping open reading frames (ORF) are present in the LOA element. In ORF1 two 'cys' motifs characteristic for gag proteins are found. The protein translated from ORF2 has similarities with retroviral pol genes. A protein databank search revealed 22% to 25% identity with the reverse transcriptase domains of retrotransposons. This region also shows the pattern of invariant amino acid residues which are most conserved in retroviral reverse transcriptases. In ORF2 an integrase specific 'cys' motif and a conserved sequence of retroviral proteases were identified. Structural similarities with LINE-like elements suggest that the LOA element represents a new non-LTR retrotransposon.
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PMID:A non-LTR retrotransposon from the Hawaiian Drosophila: the LOA element. 132 May 89

Transposable elements have been discovered in animals, plants, fungi, and protozoans which contain open reading frames similar to the gag and pol genes of retroviruses and retrotransposons but which lack long terminal repeats (LTRs). Recent experiments have shown that these non-LTR elements [also called poly(A) type and LINE-like elements] encode functional reverse transcriptase and replicate via an RNA intermediate. Based on phylogenetic analysis of their encoded reverse transcriptase sequences, the non-LTR retrotransposons are the likely progenitors of retroviruses and LTR retrotransposons. Because retroviruses and LTR retrotransposons depend upon their LTRs for key steps in both transcription and integration, the mechanisms utilized by the non-LTR retrotransposons must be fundamentally different. Internal promoter sequences have been found in several non-LTR elements that initiate transcription upstream at the first nucleotide. Current models for retrotransposition of non-LTR elements propose that the 3' ends of staggered nicks at the chromosomal insertion site serve as primers for first- and second-staggered nicks at the chromosomal insertion site serve as primers for first- and second-strand synthesis from the RNA template. These models suggest that the enzymatic machinery of non-LTR elements is likely to be responsible for the integration of SINEs and processed pseudogenes.
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PMID:Transposing without ends: the non-LTR retrotransposable elements. 132 83

We have isolated and sequenced a genomic clone from Saccharomyces cerevisiae that shows structural features of a novel retrotransposon, designated Ty4. The element is 6.2 kilobases in length, and its genetic organization of the deduced functional domains is similar to Ty1 and Ty2 and thus different from Ty3. In contrast to hitherto known Ty elements from yeast, Ty4 is flanked by long terminal tau-element repeats instead of delta or sigma sequences. Ty4 contains two overlapping open reading frames. The first open reading frame, TYA4, is 1230 base pairs long and encodes a protein with a motif found in the nucleic acid-binding gag-protein of retroviruses. The second 4395-base pair open reading frame, TYB4, encodes a polyprotein that has domains with significant homology to retroviral protease, integrase, reverse transcriptase, and RNase H, structurally arranged in that order. The deduced amino acid sequence shows the greatest similarity with Ty2 and Ty1. The overall identity of the deduced functional protein domains is 28% with Ty2, 25% with Ty1, 19% with copia from Drosophila, and 18% with Ty3. Examination of genomic DNA from several laboratory strains indicates that Ty4 is present in two to four copies. Ty4 mRNA is of low abundance as compared to other Ty retrotransposons. At the 3' end of Ty4, two "solo" delta-elements, a full length and an overlapping, truncated one, are associated.
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PMID:Ty4, a new retrotransposon from Saccharomyces cerevisiae, flanked by tau-elements. 132 82

Polymerase chain reaction analysis was used to investigate the possible role of human spumaretrovirus and oncoretroviruses (human T-cell lymphotropic virus types I [HTLV-I] and II [HTLV-II]) in multiple sclerosis. Eleven patients with relapsing-remitting multiple sclerosis in exacerbation and 11 normal blood donors were included in the study. Cerebrospinal fluid cells, peripheral blood mononuclear cells, and plasma were cocultured with allogeneic mononuclear cells for 6 weeks. Cultured cells were subjected to polymerase chain reaction analysis with primers selected for the pol and gag (human spumaretrovirus), pol and env (HTLV-I), and pol (HTLV-II) genes. Polymerase chain reaction was negative in all patient and blood donor control samples, whereas positive controls were consistently reactive with high sensitivity. No culture exhibited cytopathic effects and supernatants were negative for reverse transcriptase activity. Thus, our results do not support a role for these retroviruses in the pathogenesis of multiple sclerosis.
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PMID:No evidence for spumavirus or oncovirus infection in relapsing-remitting multiple sclerosis. 133 76

The element; Ty4 is a retrotransposon present in low copy number in the genome of Saccharomyces cerevisiae [Stucka et al., Nucleic Acids Res. 17 (1989) 4993-5001]. We have determined the complete nucleotide sequence of one such element from a particular strain and compared it to the other two elements occurring in this strain. The genomic organization of Ty4 is homologous to that found in other retrotransposons of the Ty1-copia group. The internal part of the element contains two large open reading frames (TY4A and TY4B) overlapping by 226 bp in a + 1 mode. TY4A reveals characteristics of the gag portion of retrotransposons and retroviruses, while TY4B consists of a protease, an integrase, a reverse transcriptase, and an RNase H domain (in that order). Our analyses suggest that only one of these copies might be transpositionally active. Sequence comparisons at the amino acid level show that the domains in Ty4 diverge considerably from those of other retrotransposons. The greatest similarity is seen between the reverse transcriptases (50%), the proteases (40%), and the integrases (30%) of Ty4, Ty1/2 and copia, respectively, whereas the degree of similarity for all other entities of these elements is much lower. Considering evolutionary aspects of the retrotransposons, we have to conclude that Ty4 has diverged at an early stage from the progenitors of other known retroelements and represents a novel and independent subgroup of the Ty1-copia class of retrotransposons.
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PMID:Molecular analysis of the yeast Ty4 element: homology with Ty1, copia, and plant retrotransposons. 133 37


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