title: Runt domain factor (Runx)-dependent effects on CCAAT/ enhancer-binding protein delta expression and activity in osteoblasts.
abstract: Transcription factor CCAAT/enhancer-binding protein delta (C/EBPdelta) is normally associated with acute-phase gene expression. However, it is expressed constitutively in primary osteoblast cultures where it increases insulin-like growth factor I synthesis in a cAMP-dependent way. Here we show that the 3' proximal region of the C/EBPdelta gene promoter contains a binding sequence for Runt domain factor Runx2, which is essential for osteogenesis. This region of the C/EBPdelta promoter directed high reporter gene expression in osteoblasts, and specifically bound Runx2 in osteoblast-derived nuclear extract. C/EBPdelta gene promoter activity was reduced by mutating the Runx binding sequence or by co-transfecting with Runx2 antisense expression plasmid, and was enhanced by overexpression of Runx-2. Exposure to prostaglandin E(2) increased Runx-dependent gene transactivation independently of Runx2 binding to DNA. Runx2 bound directly to the carboxyl-terminal region of C/EBPdelta itself, and its ability to drive C/EBPdelta expression was suppressed when C/EBPdelta or its carboxyl-terminal fragment was increased by overexpression. Consistent effects also occurred on C/EBPdelta-dependent increases in gene expression driven by synthetic or insulin-like growth factor I gene promoter fragments. These interactions between Runx2 and C/EBPdelta, and their activation by prostaglandin E(2), provide new evidence for their importance during skeletal remodeling, inflammatory bone disease, or fracture repair.
authors.affiliation: Department of Surgery, Plastic Surgery Section, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: McCarthy
authors.forename: C
authors.initials: C
authors.lastname: Ji
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: K K
authors.initials: KK
authors.lastname: Kim
authors.forename: M
authors.initials: M
authors.lastname: Imagawa
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.forename: M
authors.initials: M
authors.lastname: Centrella
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D016384:Consensus Sequence; D050659:Core Binding Factor Alpha 1 Subunit; D050657:Core Binding Factor alpha Subunits; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005333:Fetus; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D015345:Oligonucleotide Probes; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D050657:Core Binding Factor alpha Subunits; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D015345:Oligonucleotide Probes; D014157:Transcription Factors