title: MDM2 regulates estrogen receptor α and estrogen responsiveness in breast cancer cells.
abstract: Murine double minute clone 2 (MDM2) is a multifunctional protein, which modulates nuclear receptor-mediated transactivation. In this study, we show that MDM2 significantly enhanced estrogen receptor α (ERα) and ERα/specificity protein-mediated transactivation in MCF-7 and ZR-75 breast cancer cells. This was demonstrated by both MDM2 overexpression and knockdown experiments by RNA interference. ERα interacted with wild-type MDM2 and deletion mutants of MDM2 containing amino acids 1-342 (C-terminal deletion) and 134-490 (N-terminal deletion), but not 134-342. In contrast, only wild-type but not mutant MDM2 enhanced ERα-mediated transactivation. Protein-protein interactions in vitro were 17β-estradiol (E(2)) independent, whereas fluorescent resonance energy transfer experiments in living cells showed that E(2) enhanced ERα-MDM2 interactions. Subsequent RNA interference and mammalian two-hybrid experiments suggested that MDM2 did not directly interact with endogenous coactivators such as the steroid receptor coactivators but played a role in enhancing ERα-mediating gene expression and estrogen responsiveness through interactions with ERα.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Texas A&M University, 4466 TAMU, Veterinary Research Building 410, College Station, Texas 77843-4466, USA.
authors.forename: Kyounghyun
authors.initials: K
authors.lastname: Kim
authors.forename: Robert
authors.initials: R
authors.lastname: Burghardt
authors.forename: Rola
authors.initials: R
authors.lastname: Barhoumi
authors.forename: Syng-Ook
authors.initials: SO
authors.lastname: Lee
authors.forename: Xinyi
authors.initials: X
authors.lastname: Liu
authors.forename: Stephen
authors.initials: S
authors.lastname: Safe
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006801:Humans; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D017384:Sequence Deletion; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047628:Estrogen Receptor alpha; D004967:Estrogens; D004958:Estradiol; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2