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)

Frameshift mutants corresponding to all of the identified open reading frames of feline immunodeficiency virus, including the ORF-A gene, which has an unknown function, were constructed in vitro. Upon transfection into cells, no significant difference between the phenotypes of ORF-A mutant clones and those of wild-type clones was demonstrated. Although only ORF-A mutant virus among all mutant viruses from transfected cells showed infectivity in established T-cell lines, the replication and propagation of the ORF-A mutant virus were efficiently reduced compared with those of the wild-type virus. Moreover, the loss of the function of the ORF-A gene resulted in a severe defect in productive infection in primary peripheral blood lymphocytes both in the amount of reverse transcriptase activity produced and in core protein expression. These findings demonstrate that the ORF-A gene of feline immunodeficiency virus is required for efficient viral replication and suggest that the ORF-A gene is likely to be important for natural infection.
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PMID:The feline immunodeficiency virus ORF-A gene facilitates efficient viral replication in established T-cell lines and peripheral blood lymphocytes. 769 Apr 13

Feline immunodeficiency virus (FIV) is a member of the genus Lentivirus of the family Retroviridae. FIV can infect T lymphocytes and monocytes/macrophages in vitro and in vivo, and causes an acquired immunodeficiency syndrome-like disease in cats. Several isolates of FIV from geographically distant countries have been molecularly cloned. There is considerable heterogeneity especially in Env gene among the FIV isolates and they can be divided into two or more subgroups. Like other lentiviruses, FIV has a complex genome structure. Gag gene encodes matrix, capsid and nucleocapsid proteins, and Pol gene encodes protease, reverse transcriptase, dUTPase and integrase. The dUTPase is not present in the primate lentiviruses but present in the non-primate lentiviruses. Env gene encodes surface and transmembrane envelope glycoproteins. In addition to the structural and enzymatic proteins, at least three more genes (Vif, ORF A, Rev) are present in FIV. Vif is related to the infectivity of the cell-free viruses. Rev functions in the stability and transport of incompletely spliced viral RNAs from the nucleus to cytoplasm and is indispensable for virus replication. Although the Tat protein of the primate lentiviruses is essential for virus replication, ORF A (putative Tat gene) of FIV is not essential for virus replication in established feline T lymphoblastoid cell lines. However, the ORF A gene product is related to the efficient replication of the virus in primary peripheral blood lymphocytes. In the long terminal repeat (LTR) of FIV, there are many putative binding sites for enhancer/promoter proteins. Among these binding sites, the putative AP-1 site is important for basal promoter activity of the LTR and responsible for the T cell activation signal through protein kinase C, however the site is not required for the virus replication in established feline T lymphoblastoid cell lines. Comparative study of the molecular biology of lentiviruses revealed that the genome structure, splicing pattern and functional enhancer protein-binding sites of FIV are more similar to those of the ruminant lentiviruses than those of the primate lentiviruses.
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PMID:The genome of feline immunodeficiency virus. 812 13

We have marked a Drosophila transposable element--the LINE-like I element--with an intron-containing indicator gene inserted in place of a large deletion in the I element second ORF encompassing the reverse transcriptase domain, and this marked element was placed downstream to a potent actin promoter. An expression vector for the I element ORFs was also constructed, under the same heterologous promoter. The indicator gene contains a lacZ reporter gene the expression of which is conditioned by retrotransposition of the marked element, thus allowing detection of transposition events by testing for either beta-galactosidase expression or occurrence of spliced DNA molecules. The marked I element was introduced into Drosophila melanogaster cells in culture by transfection. Spliced DNA copies of the marked element and specifically stained beta-galactosidase-expressing cells were detected only upon co-transfection with the I expression vector, thus indicating that an ORF2-deleted element can be complemented in trans for transposition. This simple assay for retrotransposition in Drosophila cells in culture provides a tool for the rapid analysis of the mechanism of I transposition in its cis and trans sequence requirements.
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PMID:Retrotransposition of a marked Drosophila line-like I element in cells in culture. 819 Jun 41

The complete ORF-5 gene and a fragment of the ORF-7 gene from 14 different European porcine reproductive and respiratory syndrome virus (PRRSV) isolates were amplified by reverse transcriptase polymerase chain reaction (RT-PCR), and their nucleotide sequences were determined. The ORF-7 gene displayed nucleotide and amino acid identities of 94.1-99.6% and 95.3-100% among isolates from different countries. The ORF-5 gene showed higher nucleotide (87.1-99.2% identity) and amino acid (-88% identity) variability. The resulting sequences were aligned with other European and North American PRRSV strains and phylogenetic relationships among these strains were established by the maximum parsimony method. The phylogenetic trees inferred from both genes were in agreement and showed that European and North American PRRSV strains clearly represent two different genotypes. According to both trees, there is a perfect correlation between strains and the countries in which they were isolated. Additionally, the phylogenetic position of European and North American PRRSV strains within the recently proposed family Arteriviridae was also analyzed.
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PMID:Phylogenetic relationships of european strains of porcine reproductive and respiratory syndrome virus (PRRSV) inferred from DNA sequences of putative ORF-5 and ORF-7 genes. 880 83

Borna disease virus (BDV) naturally infects horses and sheep and induces progressive poliomeningoencephalomyelitis. Here, BDV recombinant proteins of the first open reading frame (ORF-I; coding for p40 nucleoprotein) and the second ORF-II (coding for p24 polymerase cofactor) were immunoblotted with plasma derived from 72 healthy (28 Arabic, 17 thoroughbred and 27 cross-bred) race horses at Tehran in Iran to detect anti-BDV antibodies. In addition, their peripheral blood mononuclear cells (PBMCs) were also examined for BDV RNA by a nested reverse transcriptase-polymerase chain reaction (RT-PCR) at ORF-II. The prevalence of BDV antibodies and/or RNA was 41.2% in Arabic, 23.5% in thoroughbred, and 33.3% in cross-bred horses, but only 17.9, 5.9, and 11.1% of them, respectively, showed positive signals for both BDV antibodies and RNA. Especially, cross-bred horses showed a higher prevalence for BDV RNA, which was detected only in females. In addition, significantly higher prevalence for BDV RNA was observed in Arabic males and thoroughbred females. The BDV prevalence did not increase with aging of the horse. Sequencing at the region of BDV derived from Iranian horses revealed a slight difference from those of Japanese horse- and European horse-derived BDVs even in the amino acid residues, although those in the three groups of Iranian horses were quite similar. Thus, the varied prevalence of BDV was observed with the horse strain or sex in Iranian horses, although BDV sequences were very similar among all three groups in Iran compared with those derived from other countries.
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PMID:Varied prevalence of Borna disease virus infection in Arabic, thoroughbred and their cross-bred horses in Iran. 889 37

A hybrid dysgenesis syndrome occurs in Drosophila virilis when males from an established laboratory strain are crossed to females obtained from the wild, causing the simultaneous mobilization of several different transposable elements. The insertion sequence responsible for the mutant phenotype of a dysgenic yellow allele has been characterized and named Penelope. In situ hybridization and Southern analyses reveal the presence of more than 30 copies of this element in the P-like parental strain, whereas Penelope is absent in all M-like strains tested. Penelope contains one 2.5-kb-long ORF that could encode products with homology to integrase and reverse transcriptase. Northern analysis and whole-mount in situ hybridization show strong induction of a 2.6-kb RNA in the ovaries of dysgenic females that is expressed at very low levels in the parental strains or in the progeny from the reciprocal cross. Injection of Penelope-containing plasmids into preblastoderm embryos of an M-like strain results in mutant progeny caused by insertion of Ulysses and perhaps other transposons, suggesting that Penelope expression might be responsible for the observed dysgenesis syndrome and the simultaneous mobilization of other transposable elements.
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PMID:Penelope, a new family of transposable elements and its possible role in hybrid dysgenesis in Drosophila virilis. 899 Jan 85

Mammalian L1 (long interspersed repeated DNA. LINE-1) retrotransposons consist of a 5' untranslated region (UTR) with regulatory properties, two protein encoding regions (ORF I, ORF II, which encodes a reverse transcriptase) and a 3' UTR. L1 elements have been evolving in mammals for > 100 million years and this process continues to generate novel L1 subfamilies in modern species. Here we characterized the youngest known subfamily in Rattus norvegicus, L1mlvi2, and unexpectedly found that this element has a dual ancestry. While its 3' UTR shares the same lineage as its nearest chronologically antecedent subfamilies, L13 and L14, its ORF I sequence does not. The L1mlvi2 ORF I was derived from an ancestral ORF I sequence that was the evolutionary precursor of the L13 and L14 ORF I. We suggest that an ancestral ORF I sequence was recruited into the modern L1mlvi2 subfamily by recombination that possibly could have resulted from template strand switching by the reverse transcriptase during L1 replication. This mechanism could also account for some of the structural features of rodent L1 5' UTR and ORF I sequences including one of the more dramatic features of L1 evolution in mammals, namely the repeated acquisition of novel 5' UTRs.
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PMID:Recombination creates novel L1 (LINE-1) elements in Rattus norvegicus. 917 13

Commelina yellow mottle virus (CoYMV) is the type member of the badnaviruses, a genus of plant pararetroviruses. The N-terminus of the polyprotein encoded by ORF III has limited similarity to known cell-to-cell movement proteins. To test the hypothesis that the N-terminus is required for viral movement, the phenotypes caused by mutations constructed in this region were determined. Similar to mutants affected in the reverse transcriptase, mutants affected in the putative movement protein were unable to cause a systemic infection. However, when the abilities of the mutated viral genomes to direct virion assembly and replication were tested using an in vitro stem-culture system, the mutants affected in the putative movement protein were found to assemble virions, whereas the reverse transcriptase mutants were unable to do so. Moreover, the putative movement protein mutants were shown to be replication competent by detection and mapping of one of the genomic discontinuities that are the hallmark of replication by reverse transcription. Thus the N-terminal region of ORF III is required for the systemic movement but not for the replication of CoYMV.
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PMID:The N-terminal portion of the 216-kDa polyprotein of Commelina yellow mottle badnavirus is required for virus movement but not for replication. 919 50

Six copies of insertion elements accumulate in the subtelomeric region immediately proximal to the telomeric repeats on Chlorella chromosome I. The elements, designated Zepps, bear the characteristic features of non-viral (LINE-like) retrotransposons, including a poly(A) tail, 5'-truncations, a retroviral reverse transcriptase-like ORF and flanking target duplications. Detailed sequence analysis of the Chlorella subtelomeric region revealed a novel mechanism of Zepp transposition; successive insertions of each Zepp element into another Zepp as a target, leaving a tandem array of their 3'-regions with poly(A) tracts facing toward the centromere. Only the most distal Zepp copy was inverted to connect its poly(A) tail with the telomeric repeats. A similar Zepp cluster but without the telomeric repeats was also found at the terminus of another Chlorella chromosome. These structures contrast with that proposed for the addition of HeT-A and TART elements to Drosophila telomeres. Expression of Zepp elements is induced by heat shock treatment. Possible roles of the subtelomeric retrotransposons in formation and maintenance of telomeres are discussed.
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PMID:Zepp, a LINE-like retrotransposon accumulated in the Chlorella telomeric region. 921 12

We have succeeded in constructing a stable full-length cDNA clone of strain H77 (genotype 1a) of hepatitis C virus (HCV). We devised a cassette vector with fixed 5' and 3' termini and constructed multiple full-length cDNA clones of H77 in a single step by cloning of the entire ORF, which was amplified by long reverse transcriptase-PCR, directly into this vector. The infectivity of two complete full-length cDNA clones was tested by the direct intrahepatic injection of a chimpanzee with RNA transcripts. However, we found no evidence for HCV replication. Sequence analysis of these and 16 additional full-length clones revealed that seven clones were defective for polyprotein synthesis, and the remaining nine clones had 6-28 amino acid mutations in the predicted polyprotein compared with the consensus sequence of H77. Next, we constructed a consensus chimera from four of the full-length cDNA clones with just two ligation steps. Injection of RNA transcripts from this consensus clone into the liver of a chimpanzee resulted in viral replication. The sequence of the virus recovered from the chimpanzee was identical to that of the injected RNA transcripts. This stable infectious molecular clone should be an important tool for developing a better understanding of the molecular biology and pathogenesis of HCV.
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PMID:Transcripts from a single full-length cDNA clone of hepatitis C virus are infectious when directly transfected into the liver of a chimpanzee. 923 47


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