Endogenously expressed estrogen receptor and coactivator AIB1 interact in MCF-7 human breast cancer cells.

Coactivators are believed to mediate estrogen-induced gene responses via interaction with estrogen receptors (ER). Currently, a major challenge is to determine the importance of each coactivator in a specific cell type and promoter context in response to a particular ligand. The potential of ER to interact with a growing list ...
of coactivators has been shown in a variety of in vitro and gene transfer assays, yet very few data have demonstrated the interaction of endogenous coactivators with ER in intact cells. We report here a ligand-specific interaction of endogenous human ER (hER) and the AIB1 coactivator in MCF-7 human breast cancer cells by using immunoprecipitation analyses. Complexes between endogenously expressed hER and AIB1 were detected in estradiol-treated cells and to a much lesser extent in cells treated with the partial agonist, monohydroxytamoxifen. We were unable to detect an hER-SRC-1 complex in our immunoprecipitations from MCF-7 cells. The in vitro-binding affinity for mouse ER interaction with AIB1 was estimated to be 40-120 nM. We conclude that AIB1 is a major coactivator for hER in MCF-7 human breast cancer cells.
Mesh Terms:
Animals, Blotting, Western, Breast Neoplasms, Estradiol, Female, Gene Expression, Histone Acetyltransferases, Humans, Mice, Nuclear Receptor Coactivator 1, Nuclear Receptor Coactivator 3, Precipitin Tests, Receptors, Estrogen, Receptors, Steroid, Selective Estrogen Receptor Modulators, Tamoxifen, Transcription Factors, Tumor Cells, Cultured
Proc. Natl. Acad. Sci. U.S.A.
Date: Nov. 07, 2000
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