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)

We investigated the feasibility of using retroviruses as vectors for transferring DNA sequences into animal cells. The thymidine kinase (tk) gene of herpes simplex virus was chosen as a convenient model. The internal BamHI fragments of a DNA clone of Moloney leukemia virus (MLV) were replaced with a purified BamHI DNA segment containing the tk gene. Chimeric genomes were created carrying the tk insert in both orientations relative to the MLV sequence. Each was transfected into TK- cells along with MLV helper virus, and TK+ colonies were obtained by selection in the presence of hypoxanthine, aminopterin, and thymidine (HAT). Virus collected from TK+-transformed, MLV producer cells passed the TK+ phenotype to TK- cells. Nonproducer cells were isolated, and TK+ transducing virus was subsequently rescued from them. The chimeric virus showed single-hit kinetics in infections. Virion and cellular RNA and cellular DNA from infected cells were all shown to contain sequences which hybridized to both MLV- and tk-specific probes. The sizes of these sequences were consistent with those predicted for the chimeric virus. In all respects studied, the chimeric MLV-tk virus behaved like known replication-defective retroviruses. These experiments suggest great general applicability of retroviruses as eucaryotic vectors.
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PMID:Adaptation of a retrovirus as a eucaryotic vector transmitting the herpes simplex virus thymidine kinase gene. 618 Mar 6

We have used site-directed mutagenesis of cloned Moloney murine leukemia virus (MuLV) DNA to define a function encoded in the 3' region of the viral pol gene and required for efficient integration of viral DNA. One mutant, MuLV-SF1, contained a single base substitution (C to T at base 4950) that resulted in an arginine to cysteine change in a region highly conserved among retroviruses. Mutant DNA, introduced into rat cells by cotransfection with a herpes simplex virus thymidine kinase gene (HSV tk), directed production of virus particles with reverse transcriptase activity. Infection of cells with these particles led to synthesis of full-length linear and circular forms of unintegrated viral DNA; however, integrated viral DNA was decreased at least by a factor of 10 when examined by DNA hybridization, and the mutant particles were less efficient then wild-type virus at establishing an infection by a factor of at least 300. Pseudotypes formed with the proteins of MuLV-SF1 and the genome of a replication defective marker MuLV, carrying the HSV tk gene, were less effective by at least a factor of 100 in producing tk+ colonies than pseudotypes formed with proteins encoded by wild-type virus. When the MuLV-SF1 pseudotypes did produce tk+ cells, most of the proviruses were integrated aberrantly. We conclude that the MuLV-SF1 pol gene is defective for a function that is required for normal integrative recombination and dissociable from DNA synthesis.
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PMID:A mutant murine leukemia virus with a single missense codon in pol is defective in a function affecting integration. 620 50

We have constructed a recombinant simian virus 40 (SV40) DNA containing a copy of the Harvey murine sarcoma virus long terminal repeat (LTR). This recombinant viral DNA was converted into an infectious SV40 virus particle and subsequently infected into NIH 3T3 cells (either uninfected or previously infected with Moloney leukemia virus). We found that this hybrid virus, SVLTR1, transforms cells with 10 to 20 times the efficiency of SV40 wild type. Southern blot analysis of these transformed cell genomic DNAs revealed that simple integration of the viral DNA within the retrovirus LTR cannot account for the enhanced transformation of the recombinant virus. A restriction fragment derived from the SVLTR-1 virus which contains an intact LTR was readily identified in a majority of the transformed cell DNAs. These results suggest that the LTR fragment which contains the attachment sites and flanking sequences for the proviral DNA duplex may be insufficient by itself to facilitate correct retrovirus integration and that some other functional element of the LTR is responsible for the increased transformation potential of this virus. We have found that a complete copy of the Harvey murine sarcoma virus LTR linked to well-defined structural genes lacking their own promoters (SV40 early region, thymidine kinase, and G418 resistance) can be effectively used to promote marker gene expression. To determine which element of the LTR served to enhance the biological activity of the recombinant virus described above, we deleted DNA sequences essential for promoter activity within the LTR. SV40 virus stocks reconstructed with this mutated copy of the Harvey murine sarcoma virus LTR still transform mouse cells at an enhanced frequency. We speculate that when the LTR is placed more than 1.5 kilobases from the SV40 early promoter, the cis-acting enhancer element within the LTR can increase the ability of the SV40 promoter to effectively operate when integrated in a murine chromosome. These data are discussed in terms of the apparent cell specificity of viral enhancer elements.
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PMID:Enhanced transformation by a simian virus 40 recombinant virus containing a Harvey murine sarcoma virus long terminal repeat. 630 72

We describe the generation of infectious retroviruses containing foreign genes by an in vivo recombination-deletion mechanism. Cotransfection into mouse cells of chimeric plasmids carrying a murine retrovirus 5' long terminal repeat and either the thymidine kinase (tk) gene of herpesvirus or the dominant selectable bacterial gene for neomycin resistance (neo), along with a clone of Moloney murine leukemia virus, results in the generation of infectious thymidine kinase or neomycin-resistant viruses. Expression of the selectable marker in these viruses can be regulated by the homologous transcriptional promoter of the gene, by the promoter contained within the Friend spleen focus-forming virus long terminal repeat, or by the simian virus 40 early region promoter. In all cases, the rescued viruses appeared to arise by recombination in vivo with Moloney murine leukemia virus sequences, resulting in the acquisition of the Moloney 3' long terminal repeat and variable amounts of the 3' adjacent Moloney genome. In two of the thymidine kinase constructs where tk was inserted 200 base pairs downstream from the long terminal repeat, the rescued viruses acquired a large part of the murine leukemia virus genome, including the region involved in packaging genomic RNA into virions. The generation of infectious neomycin-resistant virus is associated with deletions of simian virus 40 splicing and polyadenylation sequences. These results demonstrate that nonhomologous recombination and deletion events can take place in animal cells, resulting in the acquisition or removal of cis-acting sequences required for, or inhibitory to, retrovirus infectivity.
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PMID:Retrovirus transduction: generation of infectious retroviruses expressing dominant and selectable genes is associated with in vivo recombination and deletion events. 631 87

A series of deletions and insertions utilizing the herpesvirus thymidine kinase gene (tk) were constructed in the murine retrovirus Friend spleen focus-forming virus (SFFV). In all cases, the coding region for the SFFV-specific glycoprotein (gp55), which is implicated in erythroleukemic transformation, was left intact. These SFFV-TK and SFFV deletion vectors were analyzed for expression of tk and gp55 after DNA-mediated gene transfer. In addition, virus rescued by cotransfection of these vectors with Moloney murine leukemia virus was analyzed for infectious TK-transducing virus, gp55 expression, and erythroleukemia-inducing ability. The experiments demonstrated that deletions or insertions within the intron for the gp55 env gene can interfere with expression of gp55 after both DNA-mediated gene transfer and virus infection. In contrast, the gene transfer efficiency of the tk gene was unaffected in the SFFV-TK vectors, and high-titer infectious TK virus could be recovered. Revertant viruses capable of inducing erythroleukemia and expressing gp55 were generated after cotransfection of the SFFV-TK vectors with murine leukemia virus. The revertant viruses lost both tk sequences and the ability to transduce TK- fibroblasts to a TK+ phenotype. These experiments demonstrate that segregation of the TK and erythroleukemia functions can occur in retrovirus vectors which initially carry both markers.
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PMID:Retrovirus transduction: segregation of the viral transforming function and the herpes simplex virus tk gene in infectious Friend spleen focus-forming virus thymidine kinase vectors. 631 88

A recombinant plasmid containing the herpes simplex virus thymidine kinase (tk) gene, flanked on one side by two murine immunoglobulin heavy chain diversity (D) elements and on the other by two murine immunoglobulin heavy chain joining (JH) elements, was introduced into a tk- variant of a pre-B cell line transformed by Abelson murine leukemia virus. The four possible site-specific joining events between the D and JH segments within the integrated construct occurred frequently during passage of the cloned line under nonselective conditions, and deletion of the internal tk gene as a result of these joining events was, by far, the predominant mechanism of resistance to BUdR within this line. These studies demonstrate that a precise chromosomal location is not essential for the assembly of D and JH elements and provide a model system for mechanistic and genetic studies of this recombination process.
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PMID:Site-specific recombination between immunoglobulin D and JH segments that were introduced into the genome of a murine pre-B cell line. 632 46

A series of forty 5'-ester derivatives of 5-ethyl-2'-deoxyuridine (EDU) have been evaluated for their inhibitory effects on the growth and metabolism of murine leukemia L1210 cells. Several EDU esters proved as potent as EDU in their inhibitory effects on L1210 cell growth (inhibitory dose-50:5-10 micrograms/ml), suggesting that these esters were readily hydrolyzed to release the parent compound EDU. That the EDU esters had to be hydrolyzed first to EDU was further suggested by the dependence of their antiproliferative action on the thymidine kinase activity of the cells. It was further ascertained that EDU and its esters acquired their antiproliferative effects by an interaction with dCTP biosynthesis, possibly at the CDP ribonucleotide reductase step. Under conditions where thymidine was readily incorporated, we were unable to demonstrate any incorporation of EDU into L1210 cell DNA.
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PMID:Antitumor cell and antimetabolic effects of 5-ethyl-2'-deoxyuridine and 5'-substituted 5-ethyl-2'-deoxyuridine derivatives. 646 97

Two strategies have been pursued to monitor the inhibition of thymidylate (dTMP) synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45) by thymidine (dThd) analogs in intact murine leukemia L1210 cells. The first method was based on the determination of tritium release from 2'-deoxy[5-3H]uridine [( 5-3H]dUrd) or 2'-deoxy[5-3H]cytidine [( 5-3H]dCyd); the second method was based on an estimation of the amount of dCyd incorporated into DNA as dTMP. The validity of these procedures was assessed by evaluating the inhibition of thymidylate synthase in murine leukemia L1210 cells by a series of 18 dThd analogs. There was a strong correlation between the inhibitory effects of the dThd analogs on the proliferation of L1210 cells on the one hand, and (i) their inhibitory effects on tritium release from [5-3H]dCyd (r = 0.926) and (ii) their inhibitory effects on the incorporation of dCyd into DNA dTMP (r = 0.921), on the other hand. Evaluation of tritium release from [5-3H]dCyd proved to be the most convenient method that has been described so far to measure thymidylate synthase activity and to follow the inhibitory effects of thymidylate synthase inhibitors in intact L1210 cells, since this method is rapid and very sensitive, and since it proved superior to the evaluation of tritium release from [5-3H]dUrd because it circumvents possible interactions of the inhibitors with thymidine kinase activity.
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PMID:Strategies for the measurement of the inhibitory effects of thymidine analogs on the activity of thymidylate synthase in intact murine leukemia L1210 cells. 669 20

The cellular levels of the purine catabolic enzymes adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) and those for the pyrimidine activities thymidine phosphorylase and thymidine kinase isozymes have been measured concurrently in peripheral blood nucleated cells of patients with acute lymphoblastic leukaemia, chronic lymphocytic or prolymphocytic leukaemia and correlated with the spontaneous tritiated thymidine uptake of the isolated cells. Highest ADA levels occurred in T-ALL cells but considerable overlap of individual activities occurred for non-T, non-BALL, B-CLL and T-CLL cells. The levels of PNP showed no distinct discriminatory trend in cells of the lymphoid proliferative disorders examined. Thymidine phosphorylase activity was markedly reduced in T-ALL and T-CLL cells with a stepwise increase in the level of mean activities for non-T, non-B ALL, B-CLL and B-PLL cells to that of isolated normal peripheral blood lymphocytes. Spontaneous tritiated thymidine uptake of the abnormal lymphoid cells exhibited a correlation between cellular thymidine kinase isozyme 1 and elevated ADA levels. The use of ADA inhibitors together with thymidine infusion for the treatment of lymphoproliferative disorders is discussed.
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PMID:Purine and pyrimidine activities in acute and chronic lymphocytic leukaemia: relation to cellular proliferative status. 681 8

The thymidine kinase isoenzyme profile was determined in peripheral blood mononuclear cells and splenic tissue from 4 patients with hairy cell leukaemia, in order to assess the proliferative state of the hairy cell. The predominance of TK1 activity in all 4 spleens and in 2 out of 3 peripheral blood mononuclear cells examined, indicates that the hairy cell has significant proliferative capacity when compared to the neoplastic cell in other chronic lymphoproliferative disorders. It is suggested, in view of the heterogeneity in peripheral blood mononuclear TK isoenzyme types, that more extensive studies are warranted to examine the relationship between peripheral blood mononuclear TK1 activity and the occurrence of progressive disease in post-splenectomy patients.
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PMID:Fetal thymidine kinase (TK1) in hairy cell leukaemia. 683 28


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