Multiple regulatory elements and phorbol 12-O-tetradecanoate 13-acetate responsiveness of the rat placental glutathione transferase gene.
We have analyzed the cis-acting regulatory DNA elements of the placental rat glutathione S-alkyltransferase (GST-P) gene. Various regions of the 5' flanking sequence were fused with a bacterial chloramphenicol acetyltransferase gene. The transcriptional activity of each construct was determined by the transient expression assay after introduction into a hepatoma cell line. Multiple regulatory elements were identified. Two enhancing elements were located 2.5 and 2.2 kilobases upstream from the transcription start site and designated GST-P enhancers I and II (GPEI and GPEII, respectively). A consensus sequence of the phorbol 12-O-tetradecanoate 13-acetate responsive elements was present in the GPEI and at position -61. GPEII contained two of the simian virus 40 and one of the polyoma enhancer core-like sequences. A silencing element was also found 400 base pairs upstream from the cap site. In accordance with the above observation, endogenous GST-P gene was found to be stimulated when the rat fibroblast line 3Y1 was treated with phorbol 12-O-tetradecanoate 13-acetate. Phorbol 12-O-tetradecanoate 13-acetate enhanced the expression of the transfected GST-P gene to a much higher degree in HeLa cells than in the hepatoma cells, which constitutively expressed the endogenous GST-P. The results are discussed in terms of the specific derepression of GST-P gene during hepatocarcinogenesis in the rat.
Sakai
M
M
Department of Biochemistry, Faculty of Medicine, University of Tokyo, Japan.
Okuda
A
A
Muramatsu
M
M
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation / Q000187:drug effects*; D005982:Glutathione Transferase / Q000235:genetics*; D008969:Molecular Sequence Data; D010920:Placenta / Q000201:enzymology*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic; D014162:Transfection
D005982:Glutathione Transferase; D013755:Tetradecanoylphorbol Acetate