title: Down-regulation of estrogen receptor α (ERα) transcriptional activity by p27 is mediated by inhibition of ERα nuclear localization and modulation of the ERα transcriptional complex.
abstract: To investigate the role of p27 on estrogen receptor (ER)α-mediated transcription, we generated MCF-7 cells with knocked down p27 via retroviral delivery of p27 shRNA. Suppression of p27 expression in MCF-7 cells resulted in up-regulation of ERα-mediated transcription by estradiol compared to the levels in control MCF-7 cells. Accordingly, transient transfection studies in 293T cells revealed that overexpression of p27 reduced ERα-mediated transcription. The effect of p27 on ERα transcriptional activity was independent of cell cycle arrest by p27, as cell cycle arrest induced by serum starvation did not significantly affect ERα-mediated transcription. Further, we observed that p27 inhibited nuclear localization of ERα, and that p27 was associated with ERα in the cytoplasm. We also investigated the role of p27 in the modulation of ERα transcriptional activity in the nucleus. We found that p27 negatively modulated ERα transcriptional activity by inhibiting association of cyclin D1 with ERα and recruiting BRCA1 to ERα transcriptional complex. Taken together, these data suggest that p27 inhibits ERα transcriptional activity by two independent mechanisms, namely, physical nuclear exclusion of ERα, and modulation of the ERα transcriptional complex.
authors: Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea.
authors: Min Jeong
authors: MJ
authors: Jeon
authors: Wonseok
authors: W
authors: Yang
authors: Hye-Sook
authors: HS
authors: Seo
authors: Emily Shizen
authors: ES
authors: Wang
authors: Incheol
authors: I
authors: Shin
mesh_terms: D019313:BRCA1 Protein / Q000378:metabolism; D059447:Cell Cycle Checkpoints; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D061986:MCF-7 Cells; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D019313:BRCA1 Protein; D047628:Estrogen Receptor alpha; D034741:RNA, Small Interfering; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004958:Estradiol