Selective Promoter Usage of the Human Estrogen Receptor-α Gene and Its Regulation by Estrogen

• Published in: Molecular endocrinology (Baltimore, Md.) Vol. 13; no. 11; pp. 1934 - 1950
• Main Authors: Donaghue, C, Westley, B. R, May, F. E. B
• Format: Journal Article
• Language: English
• Published: United States Endocrine Society 01.11.1999
• Subjects: Breast Neoplasms - genetics; Carcinoma - genetics; Cloning, Molecular; Estrogen Receptor alpha; Estrogens - metabolism; Gene Expression Regulation; Genes, Reporter; HeLa Cells; Humans; Promoter Regions, Genetic; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Response Elements - genetics; Reverse Transcriptase Polymerase Chain Reaction; Sequence Analysis, DNA; Tumor Cells, Cultured
• ISSN: 0888-8809; 1944-9917
• DOI: 10.1210/mend.13.11.0366

Three promoters have been identified for the human estrogen receptor-α gene. The positions of promoters A and B are known whereas that of the recently identified promoter C is not. Cloning and hybridization experiments demonstrated that promoter C is located more than 21 kb upstream of promoter A. The use of the three promoters was examined in estrogen receptor-positive breast cancer cell lines, cell lines derived from other malignancies, and some normal tissues by RT-PCR and transient transfection. All estrogen-responsive breast cancer cell lines used all three promoters, apart from ZR-75 cells, which did not use promoter B in one of two sublines examined. Cell lines derived from other malignancies and other normal tissues that express lower levels of estrogen receptor-α showed more selective promoter usage. This suggests that the level of expression of estrogen receptor-α is determined by the number of promoters used, rather than the selective use of specific promoters. We also show that promoter C is used more widely than suggested by others. Analysis of a series of estrogen receptor-positive primary breast tumors showed that all three promoters were used in all the tumors. All three promoters were modulated by estrogen in estrogen-responsive breast cancer cell lines: all three promoters were down-regulated by estrogen in MCF-7 cells in which estrogens reduce receptor expression whereas all promoters used were up-regulated in T47D, ZR-75, and EFM-19 cells in which estrogens increase receptor expression. This suggests that it is the repertoire of transcription factors present within a cell rather than the selective use of a specific promoter that determines whether estrogen receptor-α expression is increased or decreased by estrogen.