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)

The lymphoproliferative disease virus of turkeys (LPDV) is the etiological agent of a rapidly developing lymphoproliferative process in turkeys. To better understand the genetic relationships of LPDV to other retroviruses we determined the nucleotide sequence of its pol gene. Comparative computer analyses of the deduced amino acid sequences of the reverse transcriptase and integrase domains within pol established that LPDV represents a distinct class of avian retroviruses that is most closely related to the avian leukemia-sarcoma viruses.
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PMID:The lymphoproliferative disease virus of turkeys represents a distinct class of avian type-C retrovirus. 128 41

Tf1, a retrotransposon from fission yeast, has LTRs and coding sequences resembling the protease, reverse transcriptase and integrase domains of retroviral pol genes. A unique aspect of Tf1 is that it contains a single open reading frame whereas other retroviruses and retrotransposons usually possess two or more open reading frames. To determine whether Tf1 can transpose, we overproduced Tf1 transcripts encoded by a plasmid copy of the element marked with a neo gene. Approximately 0.1-4.0% of the cell population acquired chromosomally inherited resistance to G418. DNA blot analysis demonstrated that such strains had acquired both Tf1 and neo specific sequences within a restriction fragment of the same size; the size of this restriction fragment varied between different isolates. Structural analysis of the cloned DNA flanking the Tf1-neo element of two transposition candidates with the same regions in the parent strain showed that the ability to grow on G418 was due to transposition of Tf1-neo and not other types of recombination events.
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PMID:Demonstration of retrotransposition of the Tf1 element in fission yeast. 131 61

The Rous sarcoma virus (RSV) integrase (IN) and the beta polypeptide (beta) of the reverse transcriptase are posttranslationally modified by phosphorylation on Ser at amino acid position 282 of IN. When IN was immunoprecipitated from RSV (Prague A strain) virions, approximately 30 to 40% of the IN molecules were phosphorylated. When IN was immunoprecipitated from a v-src deletion mutant (delta Mst-A) of RSV or from avian myeloblastosis virus (AMV), the percentage of IN molecules that were phosphorylated was significantly reduced. This reduction in phosphorylation of IN between virions was verified by [35S]Met-[35S]Cys or 32P labeling of IN, followed by immunoprecipitation analysis using antisera directed to the amino or carboxyl terminus of IN. In delta Mst-A or AMV, a nonphosphorylated, slightly truncated (at the carboxyl terminus) polypeptide was the major species of IN. The enhanced phosphorylation of IN does not appear to be a general function of transformed cells, since enhanced phosphorylation was not detected in AMV derived from viremic chickens or from a v-src deletion mutant of RSV propagated in a chemically transformed quail cell line, QT6. From these data, we conclude that v-Src is necessary for efficient phosphorylation of IN and beta.
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PMID:v-Src enhances phosphorylation at Ser-282 of the Rous sarcoma virus integrase. 131 16

High-level expression of a transpositionally competent Ty1 element fused to the inducible GAL1 promoter on a 2 microns plasmid (pGTy1) overcomes transpositional dormancy in Saccharomyces cerevisiae. To investigate the mechanisms controlling the rate of Ty1 retrotransposition, we quantitated transposition and Ty1 gene products in cells induced and uninduced for expression of pGTy1. The increase in Ty1 transposition was 45- to 125-fold greater than the increase in Ty1 RNA effected by pGTy1 induction. Translational efficiency of Ty1 RNA was not altered in transposition-induced cells, since p190TYA1-TYB1 protein synthesis increased in proportion to steady-state Ty1 RNA levels. Therefore, expression of a pGTy1 element increases the efficiency of Ty1 transposition at a posttranslational level. Galactose induction of pGTy1 enhanced TYA1 protein processing and allowed detection of processed TYB1 proteins, which are normally present at very low levels in uninduced cells. When the ability of genomic Ty1 elements to complement defined mutations in HIS3-marked pGTy1 elements was examined, mutations in the protease domain or certain mutations in the integrase domain failed to be complemented, but mutations in the reverse transcriptase domain were partially complemented by genomic Ty1 elements. Therefore, the activity of Ty1 elements in yeast cells may be limited by the availability of Ty1 protease and possibly integrase. These results suggest that Ty1 transposition is regulated at the level of protein processing and that this regulation is overcome by expression of a pGTy1 element.
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PMID:Posttranslational control of Ty1 retrotransposition occurs at the level of protein processing. 131 8

We have determined the DNA structure of the Ulysses transposable element of Drosophila virilis and found that this transposon is 10,653 bp and is flanked by two unusually large direct repeats 2136 bp long. Ulysses shows the characteristic organization of LTR-containing retrotransposons, with matrix and capsid protein domains encoded in the first open reading frame. In addition, Ulysses contains protease, reverse transcriptase, RNase H and integrase domains encoded in the second open reading frame. Ulysses lacks a third open reading frame present in some retrotransposons that could encode an env-like protein. A dendrogram analysis based on multiple alignments of the protease, reverse transcriptase, RNase H, integrase and tRNA primer binding site of all known Drosophila LTR-containing retrotransposon sequences establishes a phylogenetic relationship of Ulysses to other retrotransposons and suggests that Ulysses belongs to a new family of this type of elements.
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PMID:Ulysses transposable element of Drosophila shows high structural similarities to functional domains of retroviruses. 131 87

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

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

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

Approximately 2% of the Dictyostelium discoideum genome consists of multiple copies of a retrotransposable element termed DRE (Dictyostelium Repetitive Element). These elements have always been found integrated in a position and orientation-specific manner 50 +/- 4 nucleotides upstream of the coding region of tRNA genes (tDNAs). An intact DRE is 5.7 kb long. It carries an extensive coding region flanked by non-identical long terminal repeats (LTRs), composed of three distinct modules A, B and C. The left LTR proximal to the tRNA gene contains one or several A-modules followed by a single B-module (AnB). By contrast, the right LTR is composed of a B-module followed by a C-module (BC). Approximately 50% of the DRE elements in NC4 derivatives of D. discoideum are structurally different from the 5.7 kb DRE described above. They carry the following alterations: a) a 3.1 kb deletion in the coding region; b) two small deletions of 8 and 29 nucleotides in the B-module of the right LTR; c) a 72 bp deletion in the B-C junction; and d) three distinct point mutations within the A-module of the left LTR. The deletion in the open reading frame encompasses the putative coding regions for reverse transcriptase adn integrase. At least 60 copies of this smaller 2.4 kb DRE subtype are found in the genome of D. discoideum NC4 strains associated with tRNA genes. Thus, inspite of their lack in reverse transcriptase and integrase those 2.4 kb elements are presumably transposable and at least all isolated copies are found exclusively in the proximity of tRNA gene loci. The enzymes needed for their replication and transposition are likely to be provided by the intact 5.7 kb DREs.
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PMID:Two distinct subforms of the retrotransposable DRE element in NC4 strains of Dictyostelium discoideum. 133 70

The role of drugs inhibiting viral replication in patients infected with HIV has been confirmed. Until now only dideoxynucleosides, which are reverse transcriptase inhibitors, have demonstrated antiviral activity in humans. A number of compounds acting on other steps of the viral cycle are currently being evaluated and clinical trials are being performed. Some investigators are attempting to inhibit the binding of viral particles to target cells and their penetration into these by acting on the interaction between HIV ant the CD4 molecule. Another approach consists in the characterization of enzymatic activities which are specific of HIV, other than reverse transcriptase, such as ribonuclease H, integrase or protease, in order to prepare specific inhibitors. Attempts are made to inhibit retroviral gene expression and production of viral particles in infected cells. The development of new nucleoside analogues and drugs with mechanisms of action and toxicities different from those of zidovudine should allow in the near future combination chemotherapy of HIV infection.
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PMID:[Chemotherapy for human immunodeficiency virus infection. Current status and perspectives]. 134 31


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