Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Cultured Chinese hamster ovary cells showed no significant change in generation time or fraction in the S-phase in the presence of 1 mM N(6),O(2')-dibutyryl adenosine 3':5'-cyclic monophosphate. Growth continued for at least two generations after expression of the morphological transformation induced by this cyclic AMP analog. Despite identical growth rates, apparent rates of DNA and RNA synthesis (incorporation of [(3)H]-thymidine or [(3)H]uridine) were reduced up to 15-fold in log phase by 1 mM cyclic nucleotide. [(3)H]Deoxycytidine incorporation was much less sensitive to dibutyryl cyclic AMP. Uptake studies with [(3)H]thymidine demonstrated an inhibition of transport rate dependent on the concentration of dibutyryl cyclic AMP in the growth medium. The rate of thymidine uptake at 1 degrees was decreased 21-fold by 1 mM cyclic nucleotide; half-maximal inhibition occurred at 6 muM. At 37 degrees , the pool size of acid-soluble thymidylate was strongly reduced by 1 mM cyclic nucleotide, and synergistic reduction of the pool size was found with 0.5 mM aminophylline. Phosphorylation of the acid-soluble intracellular label was unaffected by dibutyryl cyclic AMP. Inhibition of thymidine uptake is attributed to an observed decrease in thymidine kinase activity caused by growth in 1 mM dibutyryl cyclic AMP, and possibly to a simultaneous alteration in membrane permeability. Kinase-facilitated uptake of other metabolites may be regulated in a similar fashion by cyclic AMP.
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PMID:Alteration of nucleoside transport of Chinese hamster cells by dibutyryl adenosine 3':5'-cyclic monophosphate. 434 4

Cytoplasmic thymidine kinase from cardiac muscle of the rat has been characterized. It has a pH optimum of 9.0 and a K(m) value for thymidine of 1.6mum. The sedimentation coefficient of this enzyme in sucrose gradients is 4.5S, which represents a molecular weight of approx. 69000. Thymidine kinase prepared from cardiac muscle of foetal, neonatal and adult rats is inhibited by dTTP and dTDP; there is neither inhibition nor stimulation by dTMP, dCTP, dATP, dGTP or cyclic AMP. The activity of thymidine kinase in differentiating cardiac muscle of foetal and neonatal rats declines progressively with development, reaching adult values of almost zero by the fifteenth to seventeenth day of postnatal development. This represents a 70-fold decrease in enzyme activity from 3 days before birth to 17 days after birth. The loss of thymidine kinase activity in differentiating cardiac muscle correlates temporally with the cessation of DNA biosynthesis and the loss of cytoplasmic DNA polymerase activity in this tissue.
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PMID:Thymidine kinase activity in cardiac muscle during embryomic and postnatal development. 437 15

The activities of TdR kinase2 (ATP: thymidine 5'-phosphotransferase, EC 2.7.1.21), AdR kinase (ATP: deoxyadenosine 5'-phosphotransferase, EC 2.7.1.76), GdR kinase (ATP: deoxyguanosine 5'-phosphotransferase, without EC number), ATP (Mg2+)-ase (ATP phosphohydrolase, EC 3.6.1.3), nucleoside diphosphatase (nucleoside diphosphate phosphohydrolase, EC 3.6.1.6), nucleoside phosphotransferase (AMP: deoxynucleoside phosphotransferase, EC 2.7.1.77) and ribonucleotide 5'-diphosphate reductase (EC 1.17.4.1) were assayed in mitochondria of normal and regenerating rat liver. The activities of deoxynucleoside kinases are regulated: (a) by feedback inhibition of TdR kinase with dTTP and dCTP, and GdR kinase with dGTP; (b) GdR and AdR kinases by AdR and GdR inhibition, respectively; (c) by stimulation of GdR kinase with dTDP, dTTP and dATP. The stimulatory effects are correlated with changes of ATP (Mg2+)-ase and NDP-ase activities in regenerating liver mitochondria.
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PMID:Regulation of deoxynucleoside kinase activities in rat liver mitochondria. 612 3

Epithelial cells of the rat small intestine were collected as a gradient of villus to crypt cells. Homogenates of these cells incubated with GDP-D-[14C]mannose in the presence of MnCl2 incorporated radioactivity into dolichyl mannosyl phosphate and a mixutre of dolichyl pyrophosphate oligosaccharides varying in the size of their oligosaccharide moiety. The labeled oligosaccharides formed in villus cell homogenates appeared shorter than those formed in crypt cell homogenates. The addition of dolichyl phosphate greatly stimulated the synthesis of dolichyl mannosyl phosphate. The initial rate of synthesis of dolichyl mannosyl phosphate from GDP-D-[14C]mannose and exogenous dolichyl phosphate was highest in an intermediate cell fraction having a low specific activity of sucrase and alkaline phosphatase and an intermediate specific activity of thymidine kinase. To compare the rates of dolichyl mannosyl phosphate synthesis in the different cell fractions, it was essential to control degradation of GDP-D-[14]mannose by the addition of AMP to the incubation, since villus cells degraded GDP-D-[14C]mannose much faster than crypt cells.
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PMID:Glycoprotein biosynthesis in intestinal epithelial cells during differentiation. Incorporation of [14C]mannose from GDP-[14C]mannose into dolichol derivatives. 615 73

The thymidine kinase-complex isolated from herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) is associated with the following enzyme activities:ATP:dThd (dCyd) deoxypyrimidine kinase, ATP:dTMP thymidylate kinase, ADP:dThd- and AMP:dThd 5'-phosphotransferase. In kinetic experiments it is shown that ara-AMP inhibits AMP:dThd- and ADP:dThd phosphotransferase activity, while acyclo-GMP impairs ADP:dThd phosphotransferase reaction only; the inhibition was found to be non-competitive. The functional subunit ATP:dThd kinase was not affected by either compound.
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PMID:Inhibition of the herpes simplex virus-coded thymidine kinase-complex by 9-beta-D-arabinofuranosyladenine 5'-monophosphate (ara-AMP) and 9-(2-hydroxyethoxymethyl)guanine-monophosphate (acyclo-GMP). 620 25

Recently we have described that the Herpes simplex virus (HSV)-induced thymidine kinase (TK) induces AMP- and ADP-dThd-5'-phosphotransferase activities. We now demonstrate the heterogeneity of the described activities in isoelectric focusing experiments and polyacrylamide gel electrophoresis. A TK--mutant of HSV type 1 fails to induce these activities. The activities of the type 1 enzyme complex was neutralized by an anti-HSV-serum. The TK-enzyme complex expressed in LTK--cells transformed to a TK+-phenotype by sheared HSV-1 DNA was compared with the wild type TK complex in isoelectric focusing experiments. Additionally we demonstrate that the HSV type 1 enzyme complex has thymidylate kinase activity, while the type 2 TK complex did not exhibit thymidylate kinase activity. Feedback regulation mechanisms by dTMP, dTDP and dTTP were investigated using partially purified enzyme preparations of HSV types 1 and 2 infected TK--cells.
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PMID:Analysis of the TK enzyme complex induced by HSV types 1 and 2 by means of isoelectric focusing and polyacrylamide gel electrophoresis. 628 60

To observe the effects of polyoma virus DNA on the expression of the herpes simplex virus (HSV) thymidine kinase (TK) gene early after transfer into TK-deficient mouse cells and the subsequent development of stable TK-positive transformants, we constructed a series of recombinant plasmids containing the herpes simplex virus TK gene joined with various segments of the polyoma virus genome and microinjected them into the nuclei or cytoplasm of LTK-A cells (TK(-), APRT(-)). The frequency of nucleus-injected cells expressing TK after 1 day, measured by autoradiography of cells incubated with [(3)H]thymidine, increased approximately 30-fold when the plasmids contained the polyoma virus origin of replication. The origin includes sequences with homology to the simian virus 40 origin of replication and adjoining sequences, including a recently defined transcription-enhancing sequence. After microinjection of a single origin-containing plasmid molecule per cell, TK expression was detected in approximately 50% of the injected cells. When a larger number of origin-containing plasmid molecules were injected per cell, all cells showed early TK activity. When the entire polyoma virus early region was present, neighboring uninjected cells became TK positive. When plasmids were injected into the cell cytoplasm, approximately 400 times as many molecules per cell were needed to cause early TK activity. The frequency of stable transformation observed 2 weeks after nuclear injection of 10 to 20 polyoma virus origin-containing plasmid molecules per cell was at least 2 orders of magnitude greater than with plasmids containing the TK gene alone. The greatest enhancement of stable TK transformation was obtained with plasmids containing the origin alone, when the maximum frequency of stable transformation was 5%. The addition of the coding regions for the small and medium T antigens or the entire early region significantly decreased TK transformation frequency in a copy-dependent fashion. The timing of stabilization of TK-positive transformation was analyzed by releasing hypoxanthine-aminopterin-thymidine selection pressure at various times after microinjection, culturing the cells in nonselective medium, and assaying for TK activity. Stabilization was found to occur between 3 and 6 days after nuclear injection. Cells injected with a plasmid containing the origin and the early region were examined for expression of the large T antigen with polyoma virus antitumor serum and immunofluorescent staining. The expression of the large T antigen was clearly associated with a cytopathic effect. TK-positive clones observed 2 weeks after injection of the plasmid were uniformly T antigen negative. Cytotoxicity may be the result of plasmid replication and toxic levels of T antigen or TK. In addition, expression of the large T antigen may block stabilization by preventing the integration of origin-containing plasmid molecules.
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PMID:Expression and stabilization of microinjected plasmids containing the herpes simplex virus thymidine kinase gene and polyoma virus DNA in mouse cells. 630 96

After transfection of mouse mammary tumor virus (MMTV) proviral DNA into cultured cells, the DNA is transcribed in a glucocorticoid-sensitive fashion. The large terminal repeat (LTR) region of MMTV is 1,328 nucleotides long and contains the regulatory information necessary for the hormonal response. We have constructed a MMTV LTR-thymidine kinase (tk) chimeric gene and have tested the biological activity of molecules containing various deletions in the LTR after transformation of LTK- APRT- mouse cells. In the TK+ transformants, both a LTR- tk chimeric RNA and an authentic tk RNA are correctly initiated and transcribed. The synthesis of the chimeric RNA as well as that of the tk RNA is hormonally regulated. A plasmid containing 202 nucleotides of LTR DNA 5' to the RNA initiation site is fully sensitive to glucocorticoids; 50 nucleotides still cause a residual inducibility.
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PMID:Subfragments of the large terminal repeat cause glucocorticoid-responsive expression of mouse mammary tumor virus and of an adjacent gene. 630 28

The herpes simplex virus(HSV)-coded thymidine kinase (TK) enzyme complex was isolated from HSV type 1 strain Lennette(TK+)-infected CLID (TK-) cells and was enriched by streptomycin sulfate and ammonium sulfate fractionation. This enzyme preparation was tested for dTMP:Ado (adenosine) and for dTMP:ADP phosphotransferase activities. The presence of dTMP:Ado phosphotransferase activity was proven by time-course studies with cells infected for 0-18 h, by biophysical studies in polyacrylamide gels, by affinity chromatography studies using AMP- and dTMP-Sepharose, and by immuno-neutralization experiments. The presence of dTMP:ADP phosphotransferase activity was demonstrated by kinetic experiments. These results were taken as evidence that the two functional subunits of the HSV-TK enzyme complex, AMP:dThd (deoxythymidine) phosphotransferase and ATP: dThd kinase, catalyze highly reversible enzyme reactions. New data are presented indicating that the ATP:dThd kinase is a nonspecific enzyme with respect to the nucleoside acceptor.
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PMID:Adenosine- and ADP-phosphorylating capacity of herpes simplex virus-induced thymidine kinase enzyme complex. 630 67

Mapping of the simian virus 40 (SV40) late promoter was carried out in the absence of the viral early protein, large tumor (T) antigen, and replication of the viral DNA template. SV40 late control region DNA fragments, containing specific deletions, were cloned directly upstream from the coding region of the herpes simplex virus-1 (HSV-1) thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) gene (tk). The promoter activities of the fragments were determined by measuring the tk transformation frequencies of the chimeric tk constructs in mouse L TK- APRT- (adenine phosphoribosyltransferase-negative) and human 143B TK- cell lines. The following results were obtained. (i) The SV40 control region functions with equal efficiencies in the early and late promoter orientations. (ii) A major late control element has been localized within the G+C-rich 21-base-pair (bp) repeat. Thus, in conjunction with our earlier results, the 21-bp repeat is a bidirectional promoter element functioning as a major component of both the early and late promoters and is an element that enhances the replication efficiency of SV40 DNA. (iii) Minor late promoters have been localized within the minimal replication origin and the 72-bp repeat. (iv) The minimal replication origin is not per se a constituent of the major late promoter; however, both the minimal replication origin and the 21-bp repeat are required for obtaining high levels of late gene expression observed at late times after infection by SV40. (v) The 72-bp repeat exerts a 4- to 5-fold enhancement of late promoter expression.
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PMID:Mapping of the late promoter of simian virus 40. 632 Jan 66


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