title: Orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) protein negatively regulates bone morphogenetic protein 2-induced osteoblast differentiation through suppressing runt-related gene 2 (Runx2) activity.
abstract: Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan nuclear receptor of the steroid-thyroid hormone receptor superfamily. COUP-TFII is widely expressed in multiple tissues and organs throughout embryonic development and has been shown to regulate cellular growth, differentiation, and organ development. However, the role of COUP-TFII in osteoblast differentiation has not been systematically evaluated. In the present study, COUP-TFII was strongly expressed in multipotential mesenchymal cells, and the endogenous expression level decreased during osteoblast differentiation. Overexpression of COUP-TFII inhibited bone morphogenetic protein 2 (BMP2)-induced osteoblastic gene expression. The results of alkaline phosphatase, Alizarin Red staining, and osteocalcin production assay showed that COUP-TFII overexpression blocks BMP2-induced osteoblast differentiation. In contrast, the down-regulation of COUP-TFII synergistically induced the expression of BMP2-induced osteoblastic genes and osteoblast differentiation. Furthermore, the immunoprecipitation assay showed that COUP-TFII and Runx2 physically interacted and COUP-TFII significantly impaired the Runx2-dependent activation of the osteocalcin promoter. From the ChIP assay, we found that COUP-TFII repressed DNA binding of Runx2 to the osteocalcin gene, whereas Runx2 inhibited COUP-TFII expression via direct binding to the COUP-TFII promoter. Taken together, these findings demonstrate that COUP-TFII negatively regulates osteoblast differentiation via interaction with Runx2, and during the differentiation state, BMP2-induced Runx2 represses COUP-TFII expression and promotes osteoblast differentiation.
authors.affiliation: Dental Science Research Institute and the BK21 Project, Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Kkot-Nim
authors.initials: KN
authors.lastname: Lee
authors.forename: Won-Gu
authors.initials: WG
authors.lastname: Jang
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Kim
authors.forename: Sin-Hye
authors.initials: SH
authors.lastname: Oh
authors.forename: Hye-Ju
authors.initials: HJ
authors.lastname: Son
authors.forename: Sun-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Renny
authors.initials: R
authors.lastname: Franceschi
authors.forename: Xiao-Kun
authors.initials: XK
authors.lastname: Zhang
authors.forename: Shee-Eun
authors.initials: SE
authors.lastname: Lee
authors.forename: Jeong-Tae
authors.initials: JT
authors.lastname: Koh
mesh_terms: D000818:Animals; D051837:COUP Transcription Factor II / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding
chemical_list: D051837:COUP Transcription Factor II; D050659:Core Binding Factor Alpha 1 Subunit; D020778:Matrix Metalloproteinase 2; C497587:Nr2f2 protein, mouse; C493709:RUNX2 protein, human; C493716:Runx2 protein, mouse; C522361:MMP2 protein, human; C522362:Mmp2 protein, mouse; C095569:NR2F2 protein, human