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.
Tikkanen
M K
MK
The Hospital of Loimaa, 32201 Loimaa, Finland.
Carter
D J
DJ
Harris
A M
AM
Le
H M
HM
Azorsa
D O
DO
Meltzer
P S
PS
Murdoch
F E
FE
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D001943:Breast Neoplasms; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D051548:Histone Acetyltransferases; D006801:Humans; D051379:Mice; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3; D011233:Precipitin Tests / Q000379:methods; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism; D020845:Selective Estrogen Receptor Modulators / Q000378:metabolism / Q000494:pharmacology; D013629:Tamoxifen / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D011960:Receptors, Estrogen; D011987:Receptors, Steroid; D020845:Selective Estrogen Receptor Modulators; D014157:Transcription Factors; D013629:Tamoxifen; D004958:Estradiol; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3