title: Orphan receptor COUP-TF is required for induction of retinoic acid receptor beta, growth inhibition, and apoptosis by retinoic acid in cancer cells.
abstract: Retinoic acid receptor beta (RARbeta) plays a critical role in mediating the anticancer effects of retinoids. Expression of RARbeta is highly induced by retinoic acid (RA) through a RA response element (betaRARE) that is activated by heterodimers of RARs and retinoid X receptors (RXRs). However, RARbeta induction is often lost in cancer cells despite expression of RARs and RXRs. In this study, we provide evidence that orphan receptor COUP-TF is required for induction of RARbeta expression, growth inhibition, and apoptosis by RA in cancer cells. Expression of COUP-TF correlates with RARbeta induction in a variety of cancer cell lines. In addition, stable expression of COUP-TF in COUP-TF-negative cancer cells restores induction of RARbeta expression, growth inhibition, and apoptosis by RA, whereas inhibition of COUP-TF by expression of COUP-TF antisense RNA represses the RA effects. In a transient transfection assay, COUP-TF strongly induced transcriptional activity of the RARbeta promoter in a RA- and RARalpha-dependent manner. By mutation analysis, we demonstrate that the effect of COUP-TF requires its binding to a DR-8 element present in the RARbeta promoter. The binding of COUP-TF to the DR-8 element synergistically increases the RA-dependent RARalpha transactivation function by enhancing the interaction of RARalpha with its coactivator CREB binding protein. These results demonstrate that COUP-TF, by serving as an accessory protein for RARalpha to induce RARbeta expression, plays a critical role in regulating the anticancer activities of retinoids.
authors.affiliation: Cancer Research Center, The Burnham Institute, La Jolla, California 92037, USA.
authors.forename: B
authors.initials: B
authors.lastname: Lin
authors.forename: G Q
authors.initials: GQ
authors.lastname: Chen
authors.forename: D
authors.initials: D
authors.lastname: Xiao
authors.forename: S K
authors.initials: SK
authors.lastname: Kolluri
authors.forename: X
authors.initials: X
authors.lastname: Cao
authors.forename: H
authors.initials: H
authors.lastname: Su
authors.forename: X K
authors.initials: XK
authors.lastname: Zhang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D001943:Breast Neoplasms; D051838:COUP Transcription Factor I; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D005260:Female; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D051838:COUP Transcription Factor I; D004268:DNA-Binding Proteins; C497589:NR2F1 protein, human; D011965:Receptors, Glucocorticoid; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C082925:retinoic acid receptor beta; D014212:Tretinoin