Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA-mediated gene transformation of mouse Ltk-aprt-hprt-cells was used to obtain stable, doubly selected transformants simultaneously expressing herpes virus thymidine kinase (TK) and mammalian adenine phosphoribosyltransferase (APRT). Cotransformants occurred at a frequency of 5 X 10(-6), a similar frequency for the transfer of the aprt marker has been previously observed. Isozyme and Southern blot analysis show that the TK and APRT expressed in these transformants resulted from gene transfer. For one stable cotransformant, [3H]thymidine [( 3H]TdR) selection against TK activity resulted in the loss of APRT activity as well, suggesting that these genes had become genetically linked together. Similarly selection against APRT expression resulted in the loss of a subset of the transferred herpes simplex virus tk genes. 5-Bromodeoxyuridine (BUdR) selected TK- variants differed from [3H]TdR selected TK- variants, in that they retained tk genes. However, BUdR-selected variants expressed full levels of APRT. Therefore, even though the transferred tk and aprt genes had become genetically linked together, they were, in this case, independently expressed since these cells were phenotypically TK- and APRT+.
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PMID:Genetic linkage but independent expression of functional HSV-1 tk and mammalian aprt genes after cotransfer to L cells. 298 26

Transcription of mouse mammary tumor virus DNA is stimulated by steroid hormones. The DNA sequences involved in this regulation are located in the viral long terminal repeat between positions -200 and -50 with respect to the transcription initiation site. In this region four, one distal and three proximal, in vitro binding sites for the glucocorticoid hormone-receptor complexes have been identified. We have prepared a series of 5' and 3' deletions of this region, using the exonuclease ExoIII. Combination of suitable 5' and 3' fragments enabled us to reconstitute the entire long terminal repeat with small internal deletions. The mutated long terminal repeats linked to the coding region of the Herpes simplex virus thymidine kinase gene were introduced into LTK- aprt- cells by transfection. Transcription from the mouse mammary tumor virus promoter in the presence or absence of hormone was assayed by nuclease S1 mapping. Deletion of the proximal in vitro binding sites resulted in a decrease in hormonal inducibility. When a synthetic oligonucleotide harboring the sequence of the distal in vitro binding site was inserted at the site of the proximal ones, hormone response was restored. This indicated that the distal binding site can replace the proximal ones in their hormone-regulatory function. However, insertion at the same site of an oligonucleotide containing the sequence 5' TGTTCT 3' found in all four binding sites, did not restore the hormone response, indicating that sequences flanking the TGTTCT motif are required for hormone response. Insertion of an unrelated DNA fragment at the site of the proximal binding element deletion completely abolished the hormone response. Analyses of different proximal binding-site deletion and insertion mutants suggested the presence of a transcriptional element located downstream from the most proximal hormone-receptor binding site.
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PMID:Functional analysis of the glucocorticoid regulatory elements present in the mouse mammary tumor virus long terminal repeat. A synthetic distal binding site can replace the proximal binding domain. 302 40

A mouse cell line (Ltk-aprt-) which is resistant to the anti-viral effects of interferon also has a reduced ability to synthesize metallothionein on exposure to cadmium. Like the ability to respond to interferon, cadmium-induced metallothionein synthesis is restored to wild-type levels in clones obtained by introducing a thymidine kinase gene into Ltk-aprt-cells. Transfection of other genes does not have such an effect. Since metallothionein expression is also activated by interferon the results suggest that the regulation of several genes which are responsive to interferon can be modulated by specific sequences present in the Herpes virus thymidine kinase gene.
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PMID:Activation of metallothionein expression is potentiated by DNA sequences present in the herpes simplex virus thymidine kinase gene. 303 84

A mouse fibroblast cell-line deficient in thymidine kinase (Ltk(-) aprt(-)) fails to show an anti-viral response when treated with interferon. After introduction of a viral tk gene into these cells the resultant clones showed normal responses to interferon. However, one such tk-containing clone (C6) spontaneously lost its ability to respond to interferon by inducing an antiviral state although it retained its ability to induce the enzyme oligo(2'-5' A)-synthetase. This sub-clone (6A) still expressed thymidine kinase activity but restriction endonuclease analysis indicated an alteration in the sequences flanking the exogenous viral tk gene. Our results suggest that a modification in the exogenous viral DNA sequences led to a loss of interferon sensitivity.
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PMID:Thymidine kinase genes and the induction of anti-viral responses by interferon. 619 Jun 77

We have studied the nucleoprotein structure of the herpes thymidine kinase gene introduced into mouse Ltk-aprt- cells by means of DNA-mediated gene transfer. Using the technique of Southern blotting, we examined staphylococcal digests of the nuclei from the relatively stable transformants that contain one or less integrated copies of the thymidine kinase gene per haploid genome. Out experiments show that, under selection for the active expression of this gene, it is packaged in nucleosomes with a repeat length identical to the average for the host mouse sequences.
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PMID:Nucleosomal packaging of the thymidine kinase gene of herpes simplex virus transferred into mouse cells: an actively expressed single-copy gene. 625 55

Ltk- aprt- mouse L cells were transformed to the tk+ phenotype with 10 ng of the herpes simplex virus-1 thymidine kinase (tk) gene and 20 micrograms of pBR322 or simian virus 40 (SV40) DNA. DNAs from five cloned cell lines show restriction endonuclease fragments that hybridize to both tk and pBR322 or SV40 DNA. In all of the cell lines some of these fragments also contain cellular DNA sequences. The use of carrier DNAs with defined sequences has enabled us to demonstrate that the joining of carrier and selectable gene sequences occurs in mouse cells. In one case we have been able to use the ampicillin resistance marker of pBR322 to "rescue" a recombinant plasmid. An analysis of the junction between pBR322 and tk in this plasmid suggests that a small area of homology (16 of 19 base pairs) might be involved in the recombination process.
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PMID:DNA-mediated gene transfer: recombination between cotransferred DNA sequences and recovery of recombinants in a plasmid. 628 42

The efficiency of genetic transformation of mammalian cells was analysed with respect to the kind of the transferred gene and the selective system. Plasmids pAGO and pAG60 harboring the thymidine kinase gene of Herpes simplex virus type 1 and the bacterial neomycin resistance gene, respectively, were compared concerning their ability to transform mouse Ltk-aprt- cells. Using the calcium phosphate technique the neomycin resistance gene transformed at least ten times more efficiently than the thymidine kinase gene (3 X 10(-3) versus 2 X 10(-4] whereas the difference is even more impressive following microinjection of the plasmids into the nuclei (2 X 10(-1) versus 2.5 X 10(-3]. The neomycin system also proved to be more effective in secondary gene transfer experiments and, thus, seems to be the most convenient marker for cotransfer experiments.
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PMID:The efficiency of genetic transformation of mammalian cells by transfection and microinjection depends on the transferred gene. 665 3

Transcription of mouse mammary tumor virus (MMTV) DNA is stimulated by steroid hormones. To determine the DNA sequences involved in this regulation, we constructed a plasmid containing the MMTV long terminal repeat (LTR) in front of the coding region of the herpes simplex thymidine kinase gene, from which the promoter had been removed. Portions of the LTR were removed by the nuclease Ba/31, and the deleted molecules were recloned and tested for transcriptional activity in transfections of Ltk-aprt- cells. Stably transfected cell clones were selected and hormone-dependent transcription from the MMTV promoter was studied by the S1 nuclease mapping method. The results show that DNA sequences between -105 and -204 base pairs upstream from the initiation site of viral transcription are required for glucocorticoid stimulation.
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PMID:Glucocorticoid regulation of mouse mammary tumor virus: identification of a short essential DNA region. 1087 40