title: Transcriptional coactivation of bone-specific transcription factor Cbfa1 by TAZ.
abstract: Core-binding factor 1 (Cbfa1; also called Runx2) is a transcription factor belonging to the Runt family of transcription factors that binds to an osteoblast-specific cis-acting element (OSE2) activating the expression of osteocalcin, an osteoblast-specific gene. Using the yeast two-hybrid system, we identified a transcriptional coactivator, TAZ (transcriptional coactivator with PDZ-binding motif), that binds to Cbfa1. A functional relationship between Cbfa1 and TAZ is demonstrated by the coimmunoprecipitation of TAZ by Cbfa1 and by the fact that TAZ induces a dose-dependent increase in the activity of osteocalcin promoter-luciferase constructs by Cbfa1. A dominant-negative construct of TAZ in which the coactivation domains have been deleted reduces osteocalcin gene expression down to basal levels. NIH 3T3, MC 3T3, and ROS 17/2.8 cells showed the expected nuclear localization of Cbfa1, whereas TAZ was distributed throughout the cytoplasm with some nuclear localization when transfected with either Cbfa1 or TAZ. Upon cotransfection by both Cbfa1 and TAZ, the transfected TAZ shows predominant nuclear localization. The dominant-negative construct of TAZ shows minimal nuclear localization upon cotransfection with Cbfa1. These data indicate that TAZ is a transcription coactivator for Cbfa1 and may be involved in the regulation of osteoblast differentiation.
authors.affiliation: Department of Periodontology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Cai Bin
authors.initials: CB
authors.lastname: Cui
authors.forename: Lyndon F
authors.initials: LF
authors.lastname: Cooper
authors.forename: Xiangli
authors.initials: X
authors.lastname: Yang
authors.forename: Gerard
authors.initials: G
authors.lastname: Karsenty
authors.forename: Ikramuddin
authors.initials: I
authors.lastname: Aukhil
mesh_terms: D016475:3T3 Cells; D000217:Acyltransferases; D000818:Animals; D002454:Cell Differentiation; D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D019169:Jurkat Cells; D051379:Mice; D009363:Neoplasm Proteins; D019913:Nuclear Localization Signals; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D019913:Nuclear Localization Signals; D011506:Proteins; D014157:Transcription Factors; D015675:Osteocalcin; D000217:Acyltransferases; C486363:tafazzin protein, mouse; C108675:TAFAZZIN protein, human