Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies have documented that the amount of agonist activity expressed by the antiglucocorticoid dexamethasone 21-mesylate (Dex-Mes) for tyrosine aminotransferase (TAT) induction in two rat hepatoma cell lines (Fu5-5 and HTC) is greater in Fu5-5 cells and could be varied in each cell line with changes in cell density. We have proposed that both phenomena are mediated by the binding of a trans-acting factor, the concentration or activity of which is lower in HTC cells. We have now used DNase-I hypersensitivity studies to identify a possible binding site for this factor at around -3.6 kilobases (kb) of the TAT gene. Fu5-5 and HTC cells were then stably transfected with hybrid constructs either with (3.9TATCAT) or without (2.9TATCAT) this region of the TAT gene fused up-stream of a chloramphenicol acetyltransferase (CAT) reporter gene. High levels of Dex-Mes agonist activity for the induction of CAT activity in Fu5-5 cells were seen only with the 3.9TATCAT construct, indicating that the 0.97-kb region unique to this construct controlled the high levels of Dex-Mes agonist activity. Furthermore, variations in Fu5-5 cell density caused major quantitative changes in the amount of Dex-Mes agonist activity only in cells containing the 3.9TATCAT construct, consistent with the same 0.97-kb sequences also controlling the variations in Dex-Mes agonist activity. Additional studies at high and low cell densities revealed that the modulation of Dex-Mes agonist activity for both the endogenous TAT gene and the transfected TAT/CAT gene was not due to changes in the start site of gene transcription. These studies both support our previous hypothesis that modulation of Dex-Mes agonist activity results from changes in a trans-acting factor and localize a necessary cis-acting element to sequences between -3.9 and -2.9 kb of the TAT gene. These studies, thus, define a potentially new element for glucocorticoid regulation of TAT gene transcription.
 ...
PMID:Modulation of glucocorticoid induction of stably transfected tyrosine aminotransferase gene constructs involves elements up-stream of the glucocorticoid-responsive element. 135 Jul 62

Insulin-mediated regulation of glucocorticoid-induced expression of the liver-specific gene tyrosine aminotransferase was studied in a clone of the Reuber rat hepatoma cells. Insulin inhibited dexamethasone-induced chloramphenicol acetyltransferase expression from approximately 4 kb of TAT 5' flanking sequence. The degree of this inhibition was comparable to the response of the endogenous gene. A construct of approximately 3 kbp of 5' flanking sequence exhibited no significant basal expression but retained sensitivity to glucocorticoids and to insulin inhibition of the glucocorticoid response. Results of further analysis of the insulin response in deletion constructs and constructs containing glucocorticoid responsive elements ligated to a heterologous promoter suggest that in addition to the glucocorticoid response elements a region close to the start site in the TAT promoter is necessary for insulin to inhibit glucocorticoid-mediated induction of expression.
 ...
PMID:Insulin-mediated inhibition of the induction of tyrosine aminotransferase by dexamethasone. 135 29

Synthetic ligands for steroid receptors represent important drugs in the control of fertility and in the therapy of a large variety of endocrinological diseases. In the present study we describe the establishment of different biochemical and molecular biological screening methods. We developed a microtiter plate assay for the induction of the de novo synthesis of alkaline phosphatase in T47D cells as a suitable and fast system for the measurement of actions of progestogenic and antiprogestogenic compounds. We compared several progestogenic activities with relative molar binding affinities (RBA) to the progesterone receptor. The ED50 values for the induction of alkaline phosphatase are in good accordance with RBA to the progesterone receptor. Furthermore, glucocorticoid and antiglucocorticoid effects were measured in the stable transfected breast cancer cell line ZR75/-763AGP-CAT. The construct AGP-CAT contains the glucocorticoid responsible element of the rat alpha-1-acid glycoprotein (AGP) gene with the bacterial chloramphenicol acetyltransferase (CAT) gene. The rat hepatoma Reuber cell line H4-II-E with the tyrosine aminotransferase gene is a further suitable marker of glucocorticoid action and was used as a second model for glucocorticoid activity. Thus, we demonstrated in three cell systems the antiprogestogenic and antiglucocorticoid activities of the model compound mifepristone.
 ...
PMID:Normal and stable transfected cancer cell lines: tools for a screening of progestogenic, antiprogestogenic and antiglucocorticoid substances. 788 82

The differential response of the tyrosine aminotransferase (TAT) gene to glucocorticoids and insulin in HTC cells and cell clones derived from Reuber H35 cells (FaO and Fu5.5) have been analyzed by nuclear run-on assay. It has been previously shown that clones of cells from HTC and Reuber H35 cell lines, exhibit different sensitivities for the induction of TAT mRNA and enzyme activity. The purpose of the present study was to determine whether this difference in TAT expression between hepatocytes and hepatoma cell lines occurs at the level of TAT gene transcription or mRNA stability. A study of the TAT mRNA accumulation in all cell types showed that TAT mRNA in the Reuber H35 cell clones and hepatocytes was synthesized at a higher rate than in HTC cells. However, dexamethasone induction of alpha 1 AGP mRNA and glutamine synthetase was comparable to glucocorticoid bound receptors. In addition, cycloheximide decreased the rate at which induced levels of TAT mRNA were degraded. We also show that a heterologous fusion gene constructed from 3.0 kilobases (kb) 5' to the transcription initiation site of the rat TAT gene and the bacterial chloramphenicol acetyltransferase gene (CAT) responds similarly to dexamethasone in Fu5.5 and HTC cells as determined by transient transfection assay; and insulin inhibits dexamethasone mediated transcription in Reuber H35 cells and primary adult hepatocytes. These data indicate that DNA sequences involved in the differential response of the TAT gene to hormone treatments between HTC and Reuber H35 cell lines are not located in the first 3.0 kb fragment.
 ...
PMID:Differential expression of tyrosine aminotransferase by glucocorticoids and insulin. 809 30

To investigate developmental expression of the rat tyrosine aminotransferase (TAT) gene in normal and in albino lethal mice we generated transgenic mice carrying a fusion gene of TAT 5'-sequences (11 kb) and the bacterial chloramphenicol acetyltransferase (CAT) gene. In four lines, CAT activity was found only in liver. RNA analyses on a high-expressing line showed that transgenic expression follows expression of mouse TAT mRNA: it is inducible by glucocorticoids and activated perinatally. This perinatal activation of transgene expression does not occur in lethal albino mice (c14CoS/c14CoS) which are characterized by reduced mRNA levels of several liver-specific enzymes involved in gluconeogenesis. In conclusion, the data show that the 5'-flanking region of the rat TAT gene contains elements specifying regulated expression and establish that the 5'-flanking region of the TAT gene is responsive to the enzyme deficiency characteristic of the albino lethal mice.
 ...
PMID:Perinatal activation of a tyrosine aminotransferase fusion gene does not occur in albino lethal mice. 810 68

Glucocorticoid and androgen receptors have been shown to function through the same palindromic glucocorticoid response element (GRE) and yet have differential effects on gene transcription. In this study, we examined the functional and structural relationship of the androgen and glucocorticoid receptors with the androgen responsive region (ARR) of the probasin (PB) gene containing two androgen receptor binding sites, ARBS-1 and ARBS-2. Transfection studies indicated that one copy of each cis-acting DNA element was essential for maximal androgen-induced chloramphenicol acetyltransferase (CAT) activity and that androgen selectivity was maintained when multiple copies of the minimal wild type (wt) androgen responsive region containing both ARBS-1 and ARBS-2 (-244 to -96) were subcloned in front of the thymidine kinase promoter. Furthermore, replacing the androgen response region with 1, 2 or 3 copies of either ARBS-1 or ARBS-2 restored less than 4% of the biological activity seen with the wt PB ARR. Multiple copies of either ARBS-1 or ARBS-2 did not result in glucocorticoid-induced CAT gene activity. By comparison, 1 or 2 copies of the tyrosine aminotransferase (TAT) GRE, as well as the mouse mammary tumour virus GRE, were strong inducers of CAT activity in response to both androgen and glucocorticoid treatment. In addition, band shift assays demonstrated that although the synthetic glucocorticoid receptor, GR-DNA binding domain (GR-DBD), and the synthetic androgen receptor, AR2, could interact with the TAT GRE (dissociation constants Kd of 63.9 and 14.1 respectively), only AR2 but not GR-DBD binding could be detected on ARBS-1 and ARBS-2. Our findings provide further evidence that androgen-induced regulation of gene transcription can occur through androgen-specific DNA binding sites that are distinct from the common GRE.
 ...
PMID:Selective activation of the probasin androgen-responsive region by steroid hormones. 1034 90