Contribution of proximal promoter elements to the regulation of basal and differential glutathione S-transferase P1 gene expression in human breast cancer cells.
Glutathione S-transferase P1 (GST P1-1) is normally expressed exclusively in estrogen receptor negative (ER-) but not receptor positive (ER+) cultured breast cancer cells. We examined the role of proximal promoter elements in GST P1 gene expression in MCF7 (ER+, GST P1-) and HS578T (ER-, GST P1+) breast cancer cells. Transient transfection of GST P1 promoter-CAT reporter genes confirmed that the GST P1 TRE (-69 to -60) and the adjacent distal GC box (-56 to -51) are required for basal promoter activity in both cell lines. Other studies identified differences in the GST P1 promoter activity and DNA-protein interactions between the two cell lines. Electrophoretic mobility shift assay revealed a protein-TRE interaction that is unique to nuclear proteins derived from GST P1 expressing HS578T cells. Furthermore, a putative silencer region contained within sequences -130 to -70 selectively reduced GST P1 promoter-CAT reporter gene expression in MCF7 but not HS578T cells. While this cell-line specific silencer contributed to the level of GST P1 promoter activity observed in the two cell lines, analysis of cells stably transfected with a novel genomic GST P1 minigene vector established that the silencer is insufficient to completely repress GST P1 transcription in ER+, MCF7 cells that do not normally express endogenous GST P1.
Jhaveri
M S
MS
Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1016, USA.
Morrow
C S
CS
D001943:Breast Neoplasms / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D009376:Neoplasms, Hormone-Dependent; D011401:Promoter Regions, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D004967:Estrogens; D007527:Isoenzymes; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase