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)

We have previously demonstrated in transient expression assay systems that a human multidrug resistance 1 (MDR1) promoter can be directly activated by cytotoxic anticancer agents. In this study, we examined whether the MDR1 promoter could be regulated in response to growth arrest induced by serum starvation. We have established human and rodent cell lines which stably expressed the chloramphenicol acetyltransferase (CAT) gene driven by various lengths of the MDR1, the viral thymidine kinase (TK) and the simian virus 40 (SV40) promoters. Serum starvation caused enhanced expression of CAT gene with MDR1 promoter, but not with two viral gene promoters in human cancer KB cells. Hydroxyurea activated the MDR1 promoter, but not TK and SV40 promoters. By contrast, the DNA topoisomerase II inhibitor, etoposide, equally activated the MDR1, TK and SV 40 promoters. Increased CAT gene expression by serum starvation was also specifically observed in stable transfectants of human adrenal SW-13 cell lines, but not in stable transfectants of mouse fibroblast NIH3T3 and adrenal Y-1 cell lines when the human MDR1 promoter-CAT was introduced. Etoposide, however, effectively induced CAT activity in both human and rodent cells. Assays with deletion constructs of the MDR1 promoter showed that serum starvation activated the MDR1 promoter carrying -258 approximately +121 base sequence of the promoter, but not -198 approximately +121 of the promoter. These results suggest that the expression of the MDR1 gene induced by serum starvation is regulated at the transcriptional level in a promoter sequence-specific manner in human cells.
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PMID:The human multidrug resistance 1 promoter has an element that responds to serum starvation. 155 May 97

The human multidrug resistance 1 (MDR1) gene is an SOS gene that responds to environmental stress including various anticancer agents. The chloramphenicol acetyltransferase (CAT) gene was linked to various lengths of MDR1 promoter, and these constructs were integrated into the genome of human cancer KB cells. Using these cell lines, we previously demonstrated that various environmental stimuli lead to an increased abundance of both CAT enzymatic activity and CAT mRNA in a sequence dependent manner. We examined the molecular mechanism of this stress response using actinomycin D, a potent RNA synthesis inhibitor. We found that CAT activity was significantly increased more than 10 fold by actinomycin D itself without comparable elevation of CAT mRNA. CAT induction was, however, lost in the presence of a deletion from position -136 to -76. Gel mobility shift assays showed that the specific DNA binding activity of the transacting protein, MDR-NF1/YB-1, which binds to the inverted CCAAT box, was augmented in nuclear extracts from the cells treated with actinomycin D. We also found that actinomycin D increased the steady state levels of MDR-NF1/YB-1 mRNA, which encodes the inverted CCAAT box binding protein. These results indicate that MDR-NF1/YB-1 mediates the response of the MDR1 gene to environmental stress.
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PMID:Involvement of a DNA binding protein, MDR-NF1/YB-1, in human MDR1 gene expression by actinomycin D. 790 18

The multidrug resistance 1 (MDR1) gene encodes a M(r) 170,000 membrane glycoprotein termed P-glycoprotein, which catalyzes the energy-dependent efflux of multiple anticancer agents. We investigated the activation of the MDR1 gene promoter by UV light irradiation in human cancer KB cells after both transient and stable transfection assays of the MDR1 promoter fused to the chloramphenicol acetyltransferase (CAT) gene. Following exposure to UV irradiation, CAT gene expression was about 20-fold increased. A series of promoter dissection analyses showed that two elements extending from -136 to -76 of the 5' flanking sequence and from +1 to +121 of the sequence downstream from the initiation site were required for the stress induction of MDR1 promoter activity. Gel shift assays showed that the specific DNA binding activities of the transacting protein to the MDR1 promoter were augmented in nuclear extracts from the cells treated with UV irradiation. A DNA sequence, an inverted CCAAT box, was identified that specifically bound to this protein, and mutation of this sequence abolished the binding of this protein. Two guanines in the inverted CCAAT box were found to be critical, as methylation of these guanines abrogated the binding. Nuclear run-on assay demonstrated that the transcription level was increased about 5-fold. These results suggest that the activation of the MDR1 promoter may result from transcriptional rather than posttranscriptional events. These studies will provide the basis for understanding the regulatory mechanism for appearance of the drug-resistant phenotype during cancer chemotherapy.
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PMID:Enhanced expression of the human multidrug resistance 1 gene in response to UV light irradiation. 846 53

The human multidrug resistance 1 (MDR1) gene encoding P-glycoprotein is often overexpressed in various human tumors after chemotherapy. During treatment with various chemotherapeutic agents, the MDR1 gene is activated at the transcriptional level and/or amplified, resulting in overexpression. Our previous studies demonstrated that an inverted CCAAT box (Y-box) might be a critical cis-regulatory element regulating UV or drug-induced MDR1 gene expression. We have now established various cell lines from human head and neck cancer KB cells which were stably transfected with the chloramphenicol acetyltransferase (CAT) reporter gene driven by various MDR1 promoter deletion constructs. Transient transfection of antisense YB-1 expression constructs resulted in a decrease of both YB-1 protein levels and DNA binding activity to the inverted CCAAT box, as determined by Western blot and gel mobility shift assays. The limited expression and binding activity due to expression of antisense YB-1 constructs were also observed when cells were treated with UV. CAT activity of constructs containing the Y-box was enhanced after treatment with UV irradiation as well as genotoxic agents such as cisplatin and etoposide. Moreover, this activation was reduced by 50-80% by transfection of antisense YB-1 expression constructs. In contrast, transfection of antisense YB-1 expression constructs had no effect on CAT activity driven by MDR1 promoter constructs not containing the Y-box. These data indicate that YB-1 is directly involved in MDR1 gene activation in response to genotoxic stress.
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PMID:Direct involvement of the Y-box binding protein YB-1 in genotoxic stress-induced activation of the human multidrug resistance 1 gene. 949 11