title: A repressive role for prohibitin in estrogen signaling.
abstract: Nuclear receptor-mediated gene expression is regulated by corepressors and coactivators. In this study we demonstrate that prohibitin (PHB), a potential tumor suppressor, functions as a potent transcriptional corepressor for estrogen receptor alpha (ERalpha). Overexpression of PHB inhibits ERalpha transcriptional activity, whereas depletion of endogenous PHB increases the expression of ERalpha target genes in MCF-7 breast cancer cells. Chromatin immunoprecipitation experiments demonstrate that PHB is associated with the estrogen-regulated pS2 promoter in the absence of hormone and dissociates after estradiol treatment. We demonstrate that PHB interacts with the repressor of estrogen receptor activity (REA), a protein related to PHB, to form heteromers and enhance the protein stability of both corepressors. Interestingly, the corepressor activity of PHB is cross-squelched by the coexpression of REA (and vice versa), suggesting that PHB and REA repress transcription only when they are not paired. We further demonstrate that coiled-coil domains located in the middle of PHB and REA are responsible for their heteromerization, stabilization, and cross-squelching actions. Finally, ablation of PHB function in the mouse results in early embryonic lethality, whereas mice heterozygous for the PHB null allele exhibit a hyperproliferative mammary gland phenotype. Our results indicate that PHB functions as a transcriptional corepressor for ERalpha in vitro and in vivo, and that its heteromerization with REA acts as a novel mechanism to limit its corepressor activity.
authors.affiliation: Department of Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: He
authors.forename: Qin
authors.initials: Q
authors.lastname: Feng
authors.forename: Atish
authors.initials: A
authors.lastname: Mukherjee
authors.forename: David M
authors.initials: DM
authors.lastname: Lonard
authors.forename: Francesco J
authors.initials: FJ
authors.lastname: DeMayo
authors.forename: Benita S
authors.initials: BS
authors.lastname: Katzenellenbogen
authors.forename: John P
authors.initials: JP
authors.lastname: Lydon
authors.forename: Bert W
authors.initials: BW
authors.lastname: O'Malley
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D019281:Dimerization; D047628:Estrogen Receptor alpha / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D018345:Mice, Knockout; D008957:Models, Genetic; D000091402:Prohibitins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D047628:Estrogen Receptor alpha; D004967:Estrogens; C000717328:PHB protein, human; C000717331:PHB2 protein, human; D000091402:Prohibitins; D012097:Repressor Proteins; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins