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

A transient rise in cyclic guanosine 3' : 5' monophosphate (c-GMP) in the liver was observed in rats in vivo 10--20 min after partial hepatectomy. A similar increase in c-GMP in the liver was also found in rats in vivo 15 min after infusion of TGH solution (a mixture of triiodothyronine, glucagon, and heparin). In both cases, inductions of ornithine decarboxylase [EC 4.1.1.17] and tyrosine aminotransferase [EC 2.6.1.5] were found 4 hr after the beginning of the experiments. Later, 22 hr after the surgical intervention or hormone infusion, thymidine kinase [EC 2.7.1.21] was activated and liver slices were able to incorporate [3H]thymidine into DNA. These biochemical phenomena were observed commonly in regenerating liver as well as in the liver of rats infused with TGH solution. c-GMP, but not c-AMP, could induce ornithine decarboxylase and tyrosine aminotransferase in isolated, perfused liver.
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PMID:Involvement of cyclic GMP in the initial stage of hepatocytes proliferation. 1 43

A method for producing solid tumors in rat liver or spleen by local inoculation of Yoshida sarcoma or Hirosaki sarcoma was developed by careful selection of rat strains. After development of the tumor, the liver was isolated and perfused with a mixture of calf serum and fluorocarbon. Addition of corticoid hormone to the perfusion fluid induced tyrosine aminotransferase in normal tissue of the liver and to a lesser degree in the tumor tissue. Corticoid did not cause any detectable induction of thymidine kinase in normal tissue of the liver, but caused slight but definite induction of the enzyme in the tumor tissue. Ornithine decarboxylase was induced in the normal tissue by perfusion with serum alone, even without corticoid, but no enzyme induction was observed in the tumor tissue. The low level of this enzyme found in solid tumor tissue might be due to the fact that the enzyme was measured in the late period of tumor growth, because, in experiments with ascites tumor cells, higher enzyme activities were observed in the early period of growth.
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PMID:Induction of ornithine decarboxylase, tyrosine aminotransferase, and thymidine kinase by glucocorticoid in isolated, perfused liver after tumor inoculation. 24 80

Steroid responsive elements (SRE) have been mapped at variable positions relative to the transcription start site and are often adjacent to binding sites of transcription regulatory proteins. In order to define the role of these transcriptional control sequences in the induction process, we inserted the previously defined 15-bp glucocorticoid response element (GRE) or 15-bp estrogen response element (ERE) immediately upstream of the TATA box of the thymidine kinase promoter, deleting all distal promoter elements. Both ERE and GRE confer inducibility by the respective hormone to the truncated promoter. These data suggest that the steroid receptor protein, possibly in conjunction with the TATA box binding protein, is able to form an active transcription complex. In contrast, the GRE when inserted 351 bp upstream of the start site of transcription of the tyrosine aminotransferase gene (TAT) is not capable of mediating hormone inducibility. Inducibility can be attained at this position by either two GREs or a single GRE in combination with a CCAAT motif. A cluster of point mutations in the CCAAT box abolishes hormone inducibility, strongly suggesting a synergistic action between the glucocorticoid receptor and the factor recognizing the CCAAT motif. The CCAAT box can be replaced by a CACCC box, an NF I and an SP1 binding site, thus demonstrating that synergistic action is not restricted to the CCAAT box binding protein. These combinations of a GRE with different transcription factor binding sites show a pronounced cell-type-dependent glucocorticoid induction of expression.
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PMID:Synergistic action of the glucocorticoid receptor with transcription factors. 246 58

We have previously described the inhibition of glucocorticoid-dependent transcription from the mouse mammary tumor virus long terminal repeat promoter by products of the H-ras and v-mos oncogenes. We have studied the effects of conditional oncogenes on expression of glucocorticoid-dependent indicator genes. Expression of the glucocorticoid-dependent transcription of the tyrosine aminotransferase gene was monitored in FTO-2B rat hepatoma cells during Mr 21,000 protein (p21) H-ras induction. A strong transcriptional repression of the tyrosine aminotransferase gene followed p21 H-ras expression. The sequences in a glucocorticoid-dependent promoter which are responsible for the oncogene-mediated repression could be localized to the glucocorticoid response element; a construct in which a 15-base pair glucocorticoid response element was inserted 5' of the thymidine kinase promoter exhibited the oncogene-mediated repression of transcription. We observed a strong repression of glucocorticoid-dependent promoters and promoter constructs not only in the presence of p21 H-ras and p37 v-mos but also with p60 v-src. p57 v-myc, however, had no effect. Oncogene expression is not a sufficient prerequisite for an initial repression of glucocorticoid hormone-dependent gene transcription, since even in the presence of constitutively high levels of oncogene product a transient stimulation of glucocorticoid-dependent gene expression was found. Protein synthesis inhibition experiments revealed that no hormonally induced cellular protein is needed for the oncogene-mediated repression. It seemed reasonable that this phenomenon might reflect oncogene effects on the glucocorticoid receptor. We, therefore, made measurements of the glucocorticoid receptor protein. In the presence of glucocorticoid hormone the receptor translocated rapidly from the cytoplasm to the nucleus. In normal NIH 3T3 cells, after 24-h treatments the nuclear receptor levels had declined to about 50% of those determined at 2 h and in the presence of p21 H-ras they declined to 15%. The levels of cytoplasmic receptor were not affected by p21 H-ras expression.
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PMID:Oncogene mediated repression of glucocorticoid hormone response elements and glucocorticoid receptor levels. 256 9

To define the recognition sequence of the glucocorticoid receptor and its relationship with that of the progesterone receptor, oligonucleotides derived from the glucocorticoid response element of the tyrosine aminotransferase gene were tested upstream of a heterologous promoter for their capacity to mediate effects of these two steroids. We show that a 15-base-pair sequence with partial symmetry is sufficient to confer glucocorticoid inducibility on the promoter of the herpes simplex virus thymidine kinase gene. The same 15-base-pair sequence mediates induction by progesterone. Point mutations in the recognition sequence affect inducibility by glucocorticoids and progesterone similarly. Together with the strong conservation of the sequence of the DNA-binding domain of the two receptors, these data suggest that both proteins recognize a sequence that is similar, if not the same.
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PMID:A DNA sequence of 15 base pairs is sufficient to mediate both glucocorticoid and progesterone induction of gene expression. 289 Nov 34

In order to estimate the effects of protein and amino acids on regenerating liver, the induction of enzymes involved in synthesis of DNA was studied in rats fed protein free diet. In the regenerating livers of rats of the protein free diet, increase of liver weight and DNA content were stopped 48 hours after hepatectomy, and induction of DNA synthesizing enzymes such as dCMP deaminase, ribonucleotide reductase, and thymidine kinase were depressed and shortened. On the other hand, induction of protein or RNA synthesizing enzymes such as polyamine, ornithine decarboxylase, and tyrosine aminotransferase were not depressed by protein deprivation. The results indicate that protein deprivation inhibits the DNA synthesizing enzymes specifically, and regenerating liver cells can not enter S phase of cell cycle. When rats were maintained solely by total parenteral nutrition after hepatectomy, amino acids were essential for induction of DNA synthesizing enzymes. In particular, induction of these enzymes were regulated by 7 amino acids include Val, Leu, Ile, Met, Trp, Phe, and Thr, and most of these plasma amino acid levels were depressed after hepatectomy. By administration of amino acids for 12 hours just after hepatectomy, the DNA synthesizing enzymes were almost normally induced. This suggests that amino acids administration just after hepatectomy is effective to induce the DNA synthesizing enzymes for hepatic regeneration.
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PMID:[The effects of protein and amino acids on DNA synthesis in regenerating liver]. 308 37

Modulation of gene expression by steroid hormones is mediated by receptor proteins that associate with regulatory elements of responsive genes upon binding the hormone ligand. The finding that two glucocorticoid responsive elements act cooperatively to stimulate transcription of the tyrosine aminotransferase gene prompted us to explore whether synergistic effects also occur when two different steroid hormone receptors are involved. A region of the chicken vitellogenin II gene that displays homologies to glucocorticoid and estradiol responsive elements was tested for its capability to confer estradiol and glucocorticoid inducibility to a heterologous promoter. When positioned immediately upstream of the thymidine kinase gene promoter, this element enhances expression by either steroid. Combination of both hormones results in a synergistic increase of transcription. Mutational analysis shows that sequences that show similarities of glucocorticoid and estradiol responsive elements are absolutely required for hormone induction. Analysis of the dose dependence of induction by both steroids demonstrates that half-maximal activity is observed at lower hormone concentrations when the other steroid is present in saturating amounts, which suggests that the synergistic induction observed with the combination of hormones is based on a functional interaction of the two hormone receptors.
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PMID:Synergistic action of glucocorticoid and estradiol responsive elements. 317 50

1. Relative rates of enzyme inactivation were measured in liver slices, homogenates and cytosol fractions as well as in the presence of trypsin and at acid pH. The enzymes chosen are all present in the cytosol fraction of rat liver, and have widely different degradation rate constants in vivo. 2. The inactivation rates of lactate dehydrogenase, fructose bisphosphate aldolase, glucose 6-phosphate dehydrogenase, glucokinase, phosphoenolpyruvate carboxykinase (GTP), l-serine dehydratase and thymidine kinase in liver preparations at neutral pH are in a similar order to the rate constants of degradation of these enzymes in the intact animal. 3. The two exceptions of this general correlation were tyrosine aminotransferase, which was stable in vitro but not in vivo, and glyceraldehyde phosphate dehydrogenase, which shows the reverse pattern. 4. These findings generally support the concept that the same factors are responsible for enzyme inactivation in vitro as occur in the intact tissue.
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PMID:The relative stability of liver cytosol enzymes incubated in vitro. 415 34

Novel synthetic glucocorticoid analogues were tested for receptor binding and glucocorticoid activity. They were of unusual structure, insofar as they had a 3-chloro rather than a 3-oxo function. 3-Chloro analogues of fluorinated glucocorticoids formed extremely stable complexes with the rat liver glucocorticoid receptor. 3-Chloro derivative of fluocinolone acetonide also had in vivo glucocorticoid activity. It induced tyrosine aminotransferase in the liver and repressed thymidine kinase in the thymus very effectively. It is concluded that 3-chloro analogues may retain glucocorticoid activity as well as the ability to bind to the glucocorticoid receptor protein.
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PMID:3-Chloro-1,3,5-pregnatriene derivatives with glucocorticoid activity. 614 38

The effect of 5-azacytidine on tryptophan-mediated induction of various enzymes in rat livers was analyzed. Pretreatment of animals with 5-azacytidine results in a different response of tryptophan oxygenase to tryptophan and cortisone administration. While the hormonal induction of this enzyme was not affected by the drug, the tryptophan-mediated induction was stimulated. Pretreatment of rats with 5-azacytidine resulted also in the enhancement of liver tyrosine aminotransferase activity. There was no difference between the effect of tryptophan and cortisone. Tryptophan affects also the level of thymidine kinase at various stages of liver regeneration. 5-azacytidine given 16-40 hours prior to partial hepatectomy resulted in the enhancement of thymidine kinase activity at 24 hours of regeneration.
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PMID:Tryptophan-mediated induction of hepatic enzymes stimulated by 5-azacytidine pretreatment. 616 9


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