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)

After nitrous acid mutagenesis of herpes simplex virus type 1 (HSV-1), a mutant, 1093, was isolated which, during productive infection, induced very low levels of thymidine kinase (tk). The mutant virus was found, after UV irradiation, to be unable to transform L cells lacking tk (Ltk-) to a tk+ phenotype as chararcterized by growth of the cells in a modified HAT-selective medium containing 1.6 X 10(-5) M thymidine. Cells transformed by wild-type virus grew vigorously under the same conditions. The mutant was able to transform Ltk- cells if the medium contained 10(-3) M thymidine. These transformed cells maintained their conditional character and would not grow in low concentrations of thymidine in selective medium. Therefore, this mutant is conditional on the thymidine concentration in the selection medium in its ability to transform Ltk- cells to a tk+ phenotype. The conditionally transformed cells could be supertransformed with wild-type UV-irradiated HSV-1 to a phenotype which would grow in low-thymidine selective medium. The frequency of supertransformation closely approximated the frequency of transformation of Ltk- cells by wild-type virus. Supertransformation at high frequency could not be effected by mutant 1093 or the tk- mutant B2006. These results indicate that the presence of HSV-1 genetic information in HSV-1-transformed cells does not preclude the acquisition by these cells of at least one additional HSV-1 gene, that for tk.
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PMID:Mutant of herpes simplex virus type 1 conditionally able to transform thymidine kinaseless L cells to a tk+ phenotype. 17 26

When thymidine kinase-deficient mouse cells "transformed" by in activated herpes simplex virus and expressing the viral thymidine kinase (TK) are grown in nonselective medium, there is an exponential decay in the proportion of cells that continue to express the viral enzyme. However, the viral TK can be reactivated at a frequency of approximately 1 cell in 10(6) in every population that has lost TK activity. When cells in which the viral TK has been reactivated are grown in nonselective medium, a decay in the expression of the viral enzyme occurs again at the same rate as in the initial transformed population. Studies on the reactivation of viral TK indicate that reappearance of the enzyme is not induced by the selective medium (HAT) used to detect cells in which the enzyme has reappeared. Furthermore, treatments known to induce latent viruses in other systems--eg, exposure of the cells to mutagens or cell fusion--do not affect the frequency with which viral TK is reactivated.
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PMID:Control of the expression of a herpes simplex virus thymidine kinase gene incorporated into thymidine kinase-deficient mouse cells. 19 46

Mouse L cells lacking the enzyme thymidine kinase (LMTK-) have been converted to a TK+ phenotype by infection with fragmented HSV2 strain 333 DNA. The DNA fragments used were either unique, produced by cleavage with the restriction endonucleases Eco RI and Hild III, or randomly produced by mechanical shearing. Survival in HAT medium was used initially to establish the TK+ phenotype; clones possessing the ability to grow in selective medium were picked on the basis of differing morphology and growth rates. Cytosol extracts of these clones possessed virus-specified TK activity identical to that present in cells lytically infected with HSV2, as indicated by thermolability and mobility on polyacrylamide gel electrophoresis. The transformed cells also exhibit HSV-specific immunofluorescence. Based on these transformation studies, it is possible to assign a map location to the TK gene on the HSV genome.
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PMID:Biochemical transformation of mouse cells by fragments of herpes simplex virus DNA. 19 5

In this study we investigated the expression of primate galactokinase in somatic cell hybrids between a thymidine kinase-deficient mouse cell line and two different primate cell lines, one of which was derived from African green monkey kidney cells and the other from chimpanzee fibroblasts. All the African green monkey-mouse hybrid clones, selected in HAT medium, expressed monkey galactokinase activity and contained a monkey chromosome similar to a human E-group chromosome. When these clones were backselected in medium containing 5-bromodeoxyuridine, both this chromosome and the monkey galactokinase activity were lost. All the hybrid clones between mouse and chimpanzee cells, which were selected in HAT medium, contained the chimpanzee chromosome 17 and expressed chimpanzee galactokinase activity. These results indicate that the linkage relationship between galactokinase and thymidine kinase has been maintained in 3 divergent primate species--man, chimpanzee, and Old World monkey.
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PMID:Linkage relationship between the genes for thymidine kinase and galactokinase in different primates. 19 52

New biochemically marked Djungarian hamster cell line (DX-TK-) was established. These cells are resistant to 5-bromodeoxyuridine (25 mkg/ml) and deficient in thymidine kinase activity (TK-). Due to this biochemical defect they have lost the ability to grow in HAT medium. DX-TK- cells are malignant. They grow as tumours after the inoculation to newborn Djungarian hamsters. Tumorigenecity of DX-TK- cells was decreased as compared with the parent TK+ cell line. DX-TK- cell line is a hypodiploid cell culture (26 chromosomes) with 7 chromosome markers easily identified by means of G-band staining. This line is a new model for somatic cell genetic experiments, particularly for somatic cell hybridization.
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PMID:[Production and characteristics of a Djzungarian hamster cell line (DX-TK-) resistant to 5-bromodeoxyuridine]. 21 72

DNA extracted from purified virions of equine herpesvirus type 1 (EHV-1) was examined for its transfectivity and transforming ability. The infectivity of the herpesvirus DNA was demonstrated by addition of calcium phosphate-DNA coprecipitates to monolayers of permissive horse cells, with resultant plaque formation. The efficiency of transfection (50 to 100 plaque-forming units/microgram of DNA) was reduced by treatment of the viral DNA with deoxyribonuclease or sonication but not with Pronase or antivirus neutralizing serum. When nonpermissive mouse 3T3 Cells lacking the enzyme thymidine kinase (TK-) were transfected with intact EHV-1 DNA, clones of cells transformed to the TK+ phenotype were isolated in selective HAT medium (hypoxanthine, aminopterin, thymidine), which prevents growth of the TK- parental phenotype. The efficiency of transformation ranged from one to five transformants per microgram of EHV-1 DNA. The TK activity of the biochemically transformed cells was characterized by biochemical, electrophoretic, and immunological techniques. By these criteria, the TK activity was identical to the EHV-1 TK and different from the host wild-type enzyme. In contrast to the parental TK+ 3T3 cells, the EHV-1-transformed TK+ cells were unable to grow in the presence of arabinosylthymine, a drug selectively phosphorylated by herpesvirus TKs. These results indicate that stable transfer of EHV-1 genes into nonpermissive cells can be achieved with purified viral DNA.
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PMID:Biological properties of equine herpesvirus type 1 DNA: transfectivity and transforming capacity. 21 45

BOT-2 cells (human breast tumor origin) have an impaired ability to utilize exogenous thymidine. Previous studies revealed this deficiency to be the permeation event rather than phosphorylation, since the cells have active thymidine kinase. Chromosome-mediated gene transfer was used to transfer genetic information in the form of metaphase chromosomes, from HeLa-65 cells to the BOT-2 cells, correcting the permease deficiency. Poly-L-ornithine or lipochromes were used for facilitation of chromosome uptake. After selection on HAT medium, transferant clones were isolated at a frequency of 4 x 10(-5) and 1 x 10(-5), respectively. Transferants MGP-1 and MGL-1 are stable after 18 months and have been characterized on the bases of purine and pyrimidine nucleoside uptake, relative thymidine kinase activities, alkaline phosphatase activities, and hydrocortisone-induced alkaline phosphatase activity. MGP-1 demonstrates positive thymidine uptake and incorporates radiolabeled thymidine into DNA. MGL-1 remains thymidine transport-deficient and surveys on HAT by increasing endogenous dihydrofolate reductase activity. Alkaline phosphatase activity in MGL-1 is similar to HeLa-65, 2% of that in BOT-2, and in addition, is inducible 25-30-fold by 3 micro M hydrocortisone. We have separated, genetically, a thymidine permease function from phosphorylation in cells of human origin and have transferred genetic information for the regulation of alkaline phosphatase.
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PMID:Alteration of human breast tumor cell membrane functions by chromosome-mediated gene transfer. 23 36

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)-deficient mutants of a bovine kidney cell line (MDBK) were selected following mutagenesis with ethylmethane sulfonate or ICR-170G. MDBK mutants were hybridized to thymidine kinase-deficient L cells and selected in HAT medium. Parental and hybrid cells were characterized for isozyme patterns of lactic dehydrogenase malate dehydrogenase, glucose-6-phosphate dehydrogenase, and glutamate oxalate transaminase. Chromosomes of MDBK can be distinguished from mouse L cells by configuration and by fluorescent staining with Hoechst 33-258 stain. Hybrid cells contained both MDBK and L-cell chromosomes and had elevated DNA content. MDBK cells are normally restrictive for mengovirus replication. Both permissive and restrictive hybrids were found. Our data indicate that there was preferential loss of MDBK chromosomes in the hybrid cell lines.
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PMID:Characterization of hybrids between bovine (MDBK) and mouse (L-cell) cell lines. 45 55

Interspecific human-mouse and Chinese hamster-mouse hybrids were isolated from polyethylene glycol fused cells by a new half-selection technique employing a structurally modified polyene macrolide antibiotic, amphotericin B methyl ester (AME), and HAT media. Unfused parental cells were killed as a result of innate sensitivity to AME or their genetic deficiency, absence of thymidine kinase (TK-) or hypoxanthine guanine-phosphoribosyl transferase (HGPRT-). In contrast, hybrid colonies were isolated after two to three weeks growth in three or four changes of HAT-AME media and subsequent growth in HAT media alone. The ability of hybrid cells to proliferate using this selective protocol indicates that genetic complementation resulted, and polyene antibiotic resistance was expressed as a dominant phenotypic property in the hybrids. Hybrid selection was dependent on: (1) the number of cells of each parental cell type co-cultivated; (2) the level of polyene antibiotic administered; and (3) the time interval before selection was initiated. The half-selection technique described in this report is simple to use, very effective in eliminating unfused parental cells and increases the potential types of hybrids which can be formed. Only one parental cell type need contain a biochemical defect, whereas the second parental type can be genetically normal.
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PMID:Selecting interspecific human-mouse and Chinese hamster-mouse hybrids using a new half-selection technique with a polyene antibiotic. 54 Dec 68

The structurally modified polyene antibiotic nystatin methyl ester (NME) has been utilized as a half-selection agent for isolating interspecific mouse--Syrian hamster hybrids. By using HAT media supplmented with NME we have isolated hybrid clones from polyethylene glycol-fused cultures of biochemically defective mouse (A9 or B82) and genetically normal Syrian hamster (KHK/C13) cells. Unfused parental cells were killed in HAT-NME media as a result of their genetic defect, absence of hypoxanthine guanine-phosphoribosyl transferase-HGPRT-(A9) or thymidine kinase--TK-(B82), or innate sensitivity to NME (BHK/C13). In contrast, hybrid cells proliferated and clones were isolated after 3 weeks growth in HAT-NME media, indicating the genetic complementation had occurred and polyene resistance was expressed as a dominant phenotypic property in the hybrids. The presently described technique is efficient in eliminating unfused parental cells and should prove useful in isolating other types of hybrids formed between genetically defective and normal parental cells.
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PMID:Selecting somatic cell hybrids with hat media and nystatin methyl ester. 70 4


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