Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glucocorticoid-regulatory sequences from the murine mammary tumor virus long terminal repeat (MMTV LTR) were introduced into the LTR of Moloney murine leukemia virus (M-MuLV) by recombinant DNA techniques. The site of insertion was in the M-MuLV LTR U3 region at -150 base pairs with respect to the RNA cap site. Infectious M-MuLVs carrying the altered LTRs (Mo + MMTV M-MuLVs) were recovered by transfection of proviral clones into NIH-3T3 cells. The Mo + MMTV M-MuLVs were hormonally responsive in that infection was 3 logs more efficient when performed in the presence of dexamethasone, irrespective of the orientation of the inserted MMTV sequences. However, even in the presence of hormone, the Mo + MMTV M-MuLVs were less infectious than wild-type M-MuLV. In contrast to the large effect on infectivity, dexamethasone induced virus-specific RNA levels in chronically Mo + MMTV M-MuLV-infected cells only two- to fourfold. Fusion plasmids between the altered LTRs and the bacterial chloramphenicol acetyltransferase gene allowed the investigation of LTR promoter strength by the transient chloramphenicol acetyltransferase expression assay. The chloramphenicol acetyltransferase assays indicated that the insertion of MMTV sequences into the M-MuLV LTR reduced promoter activity in the absence of glucocorticoids but that promoter activity could be induced two- to fivefold by dexamethasone. The Mo + MMTV M-MuLVs were also tested for the possibility that viral DNA synthesis or integration during initial infection was enhanced by dexamethasone. However, no significant difference was detected between cultures infected in the presence or absence of hormone. The insertion of MMTV sequences into an M-MuLV LTR deleted of its enhancer sequences did not yield infectious virus or active promoters, even in the presence of dexamethasone.
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PMID:Generation of glucocorticoid-responsive Moloney murine leukemia virus by insertion of regulatory sequences from murine mammary tumor virus into the long terminal repeat. 298 10

We report the complete 8714-nucleotide sequence of the integrated bovine leukemia virus genome and deduce the following genomic organization: 5' LTR-gag-pol-env-pXBL-3' LTR, where LTR represents a long terminal repeat and pXBL represents a region containing unidentified open reading frames. This genomic structure is similar to that of human T-cell leukemia virus. The LTR contains a putative splice donor site in the R region. The gag gene encodes a precursor protein with the form NH2-p15-p24-p12-COOH. The NH2- and COOH-terminal regions of the pol product show stronger homologies with those of avian, rather than murine, type C retrovirus, and its structure is identical to that of avian virus. The env gene encodes a surface glycoprotein (gp51) and a transmembrane protein (gp30). In contrast to the pol product, the gp30 shows stronger sequence homology with a murine, rather than avian homologue, indicating the chimeric nature of the bovine leukemia virus genome. Comparisons of the best conserved pol sequences and overall genomic organizations between several major oncoviruses allow us to propose that bovine leukemia and human T-cell leukemia viruses constitute a group, designated as type "E," of Oncovirinae.
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PMID:Complete nucleotide sequence of the genome of bovine leukemia virus: its evolutionary relationship to other retroviruses. 298 8

DNA-mediated gene transfer techniques have been used to study the effectiveness of a novel construction involving the feline leukemia virus long terminal repeat (FeLV LTR) for expressing the mouse H-2 Ld gene in mouse and human cells. In this construction, the transcription initiation (promoter) and termination (polyadenylation) functions of the FeLV LTR have been split by insertion of a promoterless H-2 gene between them. An S1 nuclease assay has been developed that makes it possible to measure accumulated LdRNA against a background of endogenous major histocompatibility antigen RNAs in mouse and human cells. In mouse cells, the H-2 Ld gene was expressed at approximately equal levels (measured as accumulated RNA) when driven either by its own promoter or by the FeLV LTR construction. In human cells, expression at the RNA level was highest when driven by the FeLV LTR. We conclude that the FeLV LTR construction is useful for expressing foreign genes in human cells.
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PMID:The promoter of the long terminal repeat of feline leukemia virus is effective for expression of a mouse H-2 histocompatibility gene in mouse and human cells. 298 2

Proviral integration near the Pim-1 gene is frequently observed in murine leukemia virus induced T-cell lymphomas in mice. Integration in the Pim-1 domain is associated with the presence of enhanced levels of a Pim-1 mRNA, which is normally expressed as a predominant 2.8 kb species at low levels in lymphoid tissues. The majority of integrations occurred in the 3' region of the Pim-1 transcription unit. This resulted in transcripts ranging in size from 2.0 to 2.6 kb, which were terminated in the 5' proviral LTR. Dependent on the site of integration up to 1300 bases of Pim-1 specific sequences were missing from the modified Pim-1 mRNA in these lymphomas.
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PMID:Proviral activation of the putative oncogene Pim-1 in MuLV induced T-cell lymphomas. 299 42

A retrovirus highly related to human T-cell leukemia virus type I (HTLV-I) was isolated from a T-cell line established from a seropositive pig-tailed monkey and the provirus genome was molecularly cloned using HTLV-I as a probe. The monkey virus (STLV) had the genomic structure of the LTR-gag-pol-env-pX-LTR. Analysis of the env-pX-LTR region revealed the 90% homology of the nucleotide sequence with that of HTLV-I in each region. This high homology of the sequence indicates that STLV is a member of the HTLV family, but apparently different from HTLV-I. This suggests that the possibility of recent interspecies transmission from monkeys to humans in the endemic area is very small. From its similarity to HTLV, STLV should be useful as an animal model in studies on natural HTLV infection and leukemogenesis of HTLV in humans.
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PMID:Sequence homology of the simian retrovirus genome with human T-cell leukemia virus type I. 299 47

Human T-cell leukemia virus type I (HTLV-I) contains a unique gene pX coding for p40 chi, and this protein was suggested to activate the transcription from the LTR of HTLV. By a similar mechanism, this viral function might be involved in immortalization of T-cells and leukemogenesis in adult T-cell leukemia induced by HTLV-I. In this communication, a part of the p40 chi was found to be tightly associated with nuclei in infected cell lines by subcellular fractionation and immunofluorescence staining.
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PMID:Association of the pX gene product of human T-cell leukemia virus type-I with nucleus. 300 74

Infection of bovines with bovine leukaemia virus (BLV) manifests itself in either of two ways: 30-70% of carriers develop persistent lymphocytosis (PL), with the viral genome integrated at a large number of different sites in the DNA of the affected B-lymphocytes, without causing any chromosomal abnormalities. Only 0,1-10% of carriers develop lymphoid tumours, which also consist of B-lymphocytes. In contrast to PL, however, they are of mono- or oligoclonal origin in terms of the integration site, which is characteristic for each tumour. All cells contain one or more copies of the viral genome, chromosomal aberrations are common and if deletions are present they are invariably found in the 5'-half of the virus DNA sequence. In both types of affected cells transcription is repressed in vivo, but transient virus production can be induced in vitro and detected by means of syncytia induction or haemagglutination. In vivo production of virus in some unknown cell is suggested by the presence of high antibody titres in infected animals, especially against the envelope glycoprotein gp51. This can be detected by various techniques such as immunodiffusion, radioimmune assay or ELISA. Monoclonal antibodies against gp51 have revealed 8 epitopes, 3 of which are recognized by neutralizing antibodies and one by a cytolytic antibody. The BLV genome, about 9 kb in size, have been cloned, and some of the information obtained on its molecular structure and function is discussed. It codes for at least 4 non-glycosylated and 2 glycoproteins. Of special interest is the recently discovered serological relationship between some of the non-glycosylated proteins and those of the human T-cell leukaemia virus. The functional role of BLV in leukaemogenesis is largely unknown. The presence of the viral genome seems to be necessary for the maintenance of the transformed state, but not its continuous expression nor an LTR-mediated promotion of transcription of cellular genes. No oncogene is carried by the virus. Although bovine leukosis is not of major economic importance, its eradication is desirable and feasible in countries with a relatively low incidence, by means of testing and elimination. For endemic situations vaccination would be preferable, and distinct possibilities exist for the development of gp51 based vaccines.
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PMID:Bovine leukaemia virus and enzootic bovine leukosis. 300 47

Human T-cell leukemia virus type I has a unique sequence pX and the product p40x was proposed to be a specific trans-acting transcriptional activator of expression of the viral gene. Recently, a second pX protein p27x-III in addition to p40x was identified; these two proteins are encoded by overlapping frames III and IV (x-lor). For determination of which product is the trans-acting activator, site-directed mutations were introduced into the pX sequence which was placed under the metallothionein promoter. On cotransfection with pLTR-CAT (a plasmid containing the LTR of HTLV-I and chloramphenicol acetyltransferase gene), only the mutations that affected p40x expression inactivated the transcriptional activation from the LTR.
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PMID:The p40x of human T-cell leukemia virus type I is a trans-acting activator of viral gene transcription. 300 3

The bovine leukemia virus, like the human T-cell leukemia viruses (HTLV-I and HTLV-II), are unusual biologically in that viral transcripts are not detected in tumors or infected tissues. The bovine leukemia virus long terminal repeat (BLV LTR) functions as a transcriptional promoter only in cell lines productively infected with BLV. Deletion mapping indicated that at least two regions of the LTR, on the 5' and 3' sides of the RNA start site, influenced gene expression. An analysis has now been made of the effects of coupling sequences from these LTR regions to a heterologous core promoter derived from the SV40 early promoter unit. Through the use of the transient expression of the bacterial chloramphenicol acetyltransferase (CAT) gene to monitor transcriptional activity in vivo, two independent, regulatory elements were identified in the BLV LTR. One was present in a fragment of 75 base pairs derived from the U3 region of the LTR and behaved much like other enhancer elements. It may be a major determinant of BLV expression in productively infected cell lines, since it enhanced transcription controlled by the heterologous core promoter only in these cells. The second element was contained in a 250-bp fragment derived from LTR sequences in the R region, located downstream from the RNA start site. Its activation of CAT expression was not dependent on BLV infection and was evident only when the fragment was located immediately downstream from the RNA start site. BLV expression thus appears to be regulated in part by a cell-specific enhancer element upstream from the core promoter and a novel sequence downstream from the RNA initiation site in the viral LTR.
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PMID:Two elements in the bovine leukemia virus long terminal repeat that regulate gene expression. 300 41

Murine monoclonal antibodies were developed against the protein products produced by murine C127 cells which had been transfected with a recombinant plasmid clone containing the human T-cell leukemia (lymphotropic) virus type I (HTLV-I) proviral DNA coding regions for part of env, px, and the 3' LTR. Four antibodies with different binding patterns were obtained. One of these antibodies, F1.6, reacted against HTLV-I infected cells but not against noninfected cell lines. This antibody also reacted with sucrose-gradient purified HTLV-I and -II particles with preferential binding against the HTLV-I preparation. The F1.6 antibody bound to two proteins of approximately 21 and 43 kDa in gradient purified HTLV-I preparations, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blots, and to a 43-kDa protein in cell lysates of HTLV-I infected cell lines; the F1.6 antibody did not bind significantly to any HTLV-II proteins in western blots. The three other antibodies F1.1, F1.2, and F1.5, recognized the same size proteins, 21 and 43 kDa in the gradient purified viral preparations of HTLV-I and in the case of the F1.2 antibody, the same size proteins in purified virus preparation of HTLV-II and -III. The F1.2 and F1.5 antibodies bound not only to purified HTLV particles but also to a variety of cellular proteins in HTLV-I infected and noninfected cells suggesting that they recognized epitopes which were shared between HTLV proteins and normal cells. The identity of the 21-kDa viral protein is most likely that of the small envelope glycoprotein. The identity of the larger protein is undetermined.
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PMID:Serological characterization of human T-cell leukemia (lymphotropic) virus, type I (HTLV-I) small envelope protein. 300 30


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