Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Jaagsiekte, or ovine pulmonary adenomatosis, is caused by a recently discovered retrovirus. The virus cannot be cultivated in vitro at present, but a procedure is described for the isolation and purification of small amounts in the form of immune complexes with IgA from affected lungs. The virion was shown to possess a 70S RNA genome which can be transcribed by an endogenous reverse transcriptase. Nine size from 94 000 to 25 000 daltons, were found in purified preparations. Using neutralization of the viral reverse transcriptase and an enzyme immunoassay as criteria, no serological relationship could be demonstrated to representatives of type B, C and C oncoviruses, or to bovine leukemia virus, maedi-visna virus of sheep or caprine arthritis-encephalitis virus.
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PMID:Isolation and preliminary characterization of the jaagsiekte retrovirus (JSRV). 667 94

A xenograft model of the human disease Langerhans cell histiocytosis (LCH) was investigated with severe combined immunodeficiency (SCID) mice. Transplantation of human LCH biopsy material into SCID mice resulted in the generation of mouse tumors resembling lymphomas. A thymoma cell line (ThyE1M6) was generated from one of these mice and found to display significant levels of Mg2+-dependent reverse transcriptase activity. Electron microscopy revealed particles with type D retroviral morphology budding from ThyE1M6 cells at a high frequency, whereas control cultures were negative. Reverse transcription-PCR of virion RNA with degenerate primers for conserved regions of various mouse, human, and primate retroviruses amplified novel sequences related to primate type D retroviruses, murine intracisternal A particles, Jaagsiekte sheep retrovirus, and murine long interspersed nuclear elements but not other retroviral classes. We demonstrate that these sequences represent a novel group of endogenous retroviruses expressed at low levels in mice but expressed at high levels in the ThyE1M6 cell line. Furthermore, we propose that the activation of endogenous retroviral elements may be associated with a high incidence of thymomas in SCID mice.
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PMID:Novel endogenous type D retroviral particles expressed at high levels in a SCID mouse thymic lymphoma. 1023 25

Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring cancer in sheep, with clinical, radiologic, and histopathologic features similar to that of human pneumonic-type bronchioloalveolar carcinoma. JSRV (Jaagsiekte Sheep RetroVirus) is the etiologic agent of this contagious lung cancer in sheep. Cells involved in the tumor derive from alveolar type II cells and Clara cells, epithelial cells of the distal respiratory tract. These cells are the major site for viral expression in JSRV-infected animals. Recent studies clearly described the oncogenic properties of the JSRV envelope protein both in vitro and in vivo. Interestingly, the cellular pathways involved in the transformation process seem to be dependent of the origin and type of the cell used. In order to investigate the specific interactions between JSRV and alveolar type II cells, we developed an in vitro experimental model in which lung epithelial cells were isolated from OPA and control lungs. Cells in culture expressed alveolar type II cell specific markers such as surfactant protein (SP)-A, SP-C, and a high alkaline phosphatase activity. Alveolar Type II cells derived from tumoral lungs showed a proliferative advantage and expressed the JSRV virus. The reverse transcriptase activity decreased over passages in monolayer culture conditions, but was efficiently maintained in three-dimensional culture conditions. We thus report on the first in vitro system whereby alveolar type II cells from OPA were efficiently maintained in culture and stably expressed JSRV. This novel experimental model will set up the stage for elucidating lung epithelial transformation in the JSRV-induced tumor.
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PMID:Alveolar type II cells isolated from pulmonary adenocarcinoma: a model for JSRV expression in vitro. 1715 59

A proportion of human pulmonary adenocarcinomas has been shown previously to express an antigen related to the Gag protein of a betaretrovirus, Jaagsiekte sheep retrovirus, that causes ovine pulmonary adenocarcinoma. To investigate further the hypothesis that a retrovirus might be present in human lung adenocarcinoma, we examined specimens from patients with lung cancer for evidence of retroviral infection by immunohistochemistry, reverse transcriptase-polymerase chain reaction, immunoblotting and cDNA library screening. Thirty-eight percent of the tumor samples analyzed were positive by immunohistochemistry for Gag-related antigen of Jaagsiekte sheep retrovirus. However, this antigen was not detected by immunoblotting using the same antiserum. In addition, plasma samples from the patients did not contain antibodies reacting with Gag proteins from Jaagsiekte sheep retrovirus or other betaretroviruses on immunoblots. Reverse transcriptase-polymerase chain reaction identified the expression of endogenous betaretroviruses in tumor tissue and in normal lung tissue, but no specific provirus was associated with tumor. Expression library screening did not identify the Gag-reactive antigen. This study has confirmed the expression of a Jaagsiekte sheep retrovirus Gag-related antigen in some human lung tumors but additional evidence of betaretroviral infection was not obtained. While these data do not rule out a role for a retrovirus in human pulmonary adenocarcinomas, they suggest that, if such a virus is present, it is unrelated to known betaretroviruses.
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PMID:Absence of markers of betaretrovirus infection in human pulmonary adenocarcinoma. 2082 71