Regulation mechanisms of glutathione transferase gene expression during hepatocarcinogenesis
| Project/Area Number |
05671820
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biological pharmacy
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| Research Institution | Osaka University |
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Principal Investigator |
IMAGAWA Masayoshi Osaka University, Fac. of Pharm. Sci., Associate Professor, 薬学部, 助教授 (20136823)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1993: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Glutathione transferase / Hepatocellular carcinoma / Chemical carcinogenesis / Enhancer / Silencer / Gene expression / Transgenic rats |
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| Research Abstract |
Rat glutathione transferase P (GST-P) is expressed at low levels in normal liver but becomes highly expressed in hyperplastic nodules and in hepatocellular carcinomas during chemical hepatocarcinogenesis. To understand the regulation mechanisms of this gene, we characterized the 5'-flanking region and found that GST-P gene is regulated by at least two elements : one a strong enhancer (GPEI) and the other a silencer.
We carried out carcinogenesis experiments using transgenic rats harboring chloramphenicol acetyltransferase (CAT) reporter gene with -2900 to +59of the GST-P gene. Liver foci and nodules produced by chemical carcinogens were found to express high levels CAT activity by both CAT assay and immunohistochemical study, while normal liver cells did not express any CAT activity. These results demonstrate that the GST-P gene is trans-activated locus-independently during rat hepatocarcinogenesis. Moreover, the similar results were obtained using transgenic rats carrying GPEI-CAT,indicating that GPEI is an important cis-elements for activation of GST-P gene during hepatocarcinogenesis.
We have also identified a silencer element at 300bp upstream from the cap site. There are several cis-elements in this region and at least three trans-acting factors bind to these elements. We purified SF-A (Silencer Factor A) binds to several regions in this silencer, and determined the partial amino acid sequence. Interestingly, SF-A seemed to be related protein to NF1 (Nuclear Factor 1) which is activator for transcription and DNA replication. Another factor SF-B (Silencer Factor B) has been cloned and found to be same as LIP (Liver Inhibitory Protein) which is a competitor for LAP (Liver Actovator Protein). By transfection assay using GAL4 DNA binding domain, however, we found LIP is not only a competitor but a direct repressor.
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Report
(3 results)
Research Products
(16 results)
