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)

In this work, we have studied the activity of a tetracycline modulatable trans-activator (tTA) generated by fusing the DNA binding domain of the tetracycline repressor to the trans-activation domain of the Herpes simplex virus protein 16 (HSV VP16) (plasmid pUHD15-1Neo). In the three different cell lines studied (HTC, rat hepatoma; T47D, human breast cancer; SK-N-BE, human neuroblastoma), the expression of the luciferase gene under the control of a tetracycline operator sequence (plasmid pUHC13-3) was used as a control of the incorporation and the functionality of the trans-activator. Clones selected from these cells responded in a time and dose-dependent manner to the withdrawal of tetracycline. In all these clones, the tTA trans-activator not only modulates the activity of the luciferase gene, but also modulates the activity of a number of endogenous proteins, including C/EBP beta, the glucocorticoid receptor (GR), and SP1. In the transfected cells, the level of these transcription factors was strongly inhibited in the presence of tetracycline and was highly increased after tetracycline removal. Electrophoresis mobility shift assay (EMSA) and footprint experiments proved that the induced proteins are perfectly efficient in binding the DNA. Their transcriptional activity was also determined. In HTC/A9 cells, the level of the chloramphenicol acetyltransferase (CAT) expression driven by the promoter of the alpha 1-glycoprotein (AGP) gene was strongly enhanced at 72-84 hr following removal of tetracycline from the growth media. The accumulation of the endogenous AGP mRNA also increased at 84 hr. In the T47D/TA11 and SK-N-BE/C2.6 cells, a general activation of protein synthesis was also evidenced.
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PMID:Specificity of action of a herpes virus VP16/tetracycline-dependent trans-activator in mammalian cell cultures. 764 13

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.
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PMID:Differential expression of tyrosine aminotransferase by glucocorticoids and insulin. 809 30