Estrogen receptor-alpha interaction with the CREB binding protein coactivator is regulated by the cellular environment.
The p160 coactivators, steroid receptor coactivator-1 (SRC-1), transcriptional intermediary factor-2 (TIF2) and receptor-associated coactivator-3 (RAC3), as well as the coactivator/integrator CBP, mediate estrogen receptor-alpha (ERalpha)-dependent gene expression. Although these coactivators are widely expressed, ERalpha transcriptional activity is cell-type dependent. In this study, we investigated ERalpha interaction with p160 coactivators and CBP in HeLa and HepG2 cell lines. Basal and estradiol (E2)-dependent interactions between the ERalpha ligand-binding domain (LBD) and SRC-1, TIF2 or RAC3 were observed in HeLa and HepG2 cells. The extents of hormone-dependent interactions were similar and interactions between each of the p160 coactivators and the ERalpha LBD were not enhanced by 4-hydroxytamoxifen in either cell type. In contrast to the situation for p160 coactivators, E2-dependent interaction of the ERalpha LBD with CBP or p300 was detected in HeLa but not HepG2 cells by mammalian two-hybrid and coimmunoprecipitation assays, indicating that the cellular environment modulates ERalpha-CBP/p300 interaction. Furthermore, interactions between CBP and p160 coactivators are much more robust in HeLa than HepG2 cells suggesting that poor CBP-p160 interactions are insufficient to support ERalpha-CBP-p160 ternary complexes important for nuclear receptor-CBP interactions. Alterations in p160 coactivators or CBP expression between these two cell types did not account for differences in ERalpha-p160-CBP interactions. Taken together, these data revealed the influence of cellular environment on ERalpha-CBP/p300 interactions, as well as CBP-p160 coactivator binding, and suggest that these differences may contribute to the cell specificity of ERalpha-dependent gene expression.
Jaber
B M
BM
Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
Mukopadhyay
R
R
Smith
C L
CL
D050882:CREB-Binding Protein; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D006367:HeLa Cells; D051548:Histone Acetyltransferases; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D056920:Nuclear Receptor Coactivator 1; D051958:Nuclear Receptor Coactivator 2; D056921:Nuclear Receptor Coactivator 3; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
D047628:Estrogen Receptor alpha; C498001:NCOA2 protein, human; D009687:Nuclear Proteins; D051958:Nuclear Receptor Coactivator 2; D015534:Trans-Activators; D014157:Transcription Factors; D013629:Tamoxifen; C016601:afimoxifene; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3