Endogenously Expressed Estrogen Receptor and Coactivator AIB1 Interact in MCF-7 Human Breast Cancer Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 97; no. 23; pp. 12536 - 12540
• Main Authors: Tikkanen, Minna K., Carter, Damien J., Harris, Alana M., Le, Hung M., Azorsa, David O., Meltzer, Paul S., Murdoch, Fern E.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 07.11.2000; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: AIB1 gene; Animals; Antibodies; Biochemistry; Biological Sciences; Blotting, Western - methods; Breast cancer; Breast Neoplasms; Breasts; Cell lines; Cell nucleus; Cells; Epithelial cells; Estradiol - metabolism; Estradiol - pharmacology; Estrogens; Female; Gene Expression; Genes; Histone Acetyltransferases; Humans; Immunoprecipitation; Ligands; Mice; monohydroxytamoxifen; Nuclear Receptor Coactivator 1; Nuclear Receptor Coactivator 3; Precipitin Tests - methods; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Receptors, Steroid - metabolism; Selective Estrogen Receptor Modulators - metabolism; Selective Estrogen Receptor Modulators - pharmacology; Tamoxifen - metabolism; Tamoxifen - pharmacology; Transcription Factors - genetics; Transcription Factors - metabolism; Tumor Cells, Cultured; Vanadates
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.220427297

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.