Selective promoter usage of the human estrogen receptor-alpha gene and its regulation by estrogen.
Three promoters have been identified for the human estrogen receptor-alpha 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-alpha showed more selective promoter usage. This suggests that the level of expression of estrogen receptor-alpha 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 upregulated 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-alpha expression is increased or decreased by estrogen.
Donaghue
C
C
University Department of Pathology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.
Westley
B R
BR
May
F E
FE
D001943:Breast Neoplasms / Q000235:genetics; D002277:Carcinoma / Q000235:genetics; D003001:Cloning, Molecular; D047628:Estrogen Receptor alpha; D004967:Estrogens / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000235:genetics* / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014407:Tumor Cells, Cultured
D047628:Estrogen Receptor alpha; D004967:Estrogens; D011960:Receptors, Estrogen