title: Tumor necrosis factor-α enhances the transcription of Smad ubiquitination regulatory factor 1 in an activating protein-1- and Runx2-dependent manner.
abstract: Smad ubiquitination regulatory factor 1 (Smurf1) is an E3 ubiquitin ligase that negatively regulates osteoblast differentiation. Although tumor necrosis factor-α (TNF-α) has been shown to increase Smurf1 expression, the details of the regulatory mechanisms remain unclear. Here, we investigated the molecular mechanism by which TNF-α stimulates Smurf1 expression in C2C12 and primary cultured mouse calvarial cells. TNF-α treatment rapidly induced the activation of NF-κB and MAPKs. Smurf1 induction by TNF-α was blocked by the inhibition of JNK or ERK, while the inhibition of NF-κB and p38 MAPK had no effect on Smurf1 induction. TNF-α treatment or c-Jun overexpression enhanced the activity of a luciferase reporter that contained a 2.7 kb mouse Smurf1 promoter sequence. Site-directed mutagenesis of the Smurf1 reporter and chromatin immunoprecipitation analysis demonstrated that the activating protein-1 (AP-1) binding motif at -922 bp on the mouse Smurf1 promoter mediated TNF-α/JNK/AP-1-stimulated Smurf1 transcription. Interestingly, Smurf1 expression was not observed in Runx2-null mouse calvarial cells. When Runx2 was ectopically expressed in these cells, the basal and TNF-α-induced expression of Smurf1 was restored. Overexpression of Runx2 transactivated the Smurf1 promoter in a dose-dependent manner. Reporter and chromatin immunoprecipitation assays demonstrated that the Runx2-binding motif at -202 bp functioned in Runx2-mediated Smurf1 expression. ERK activation by TNF-α treatment or constitutively active MEK1 overexpression increased Smurf1 expression in a Runx2-dependent manner. These results suggest that the JNK/AP-1 and ERK/Runx2 signaling pathways mediate TNF-α-dependent Smurf1 transcription.
authors.affiliation: Department of Molecular Genetics, School of Dentistry, Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Hye-Lim
authors.initials: HL
authors.lastname: Lee
authors.forename: Tacghee
authors.initials: T
authors.lastname: Yi
authors.forename: Kyunghwa
authors.initials: K
authors.lastname: Baek
authors.forename: Arang
authors.initials: A
authors.lastname: Kwon
authors.forename: Hyo Rin
authors.initials: HR
authors.lastname: Hwang
authors.forename: Abdul S
authors.initials: AS
authors.lastname: Qadir
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Park
authors.forename: Kyung Mi
authors.initials: KM
authors.lastname: Woo
authors.forename: Hyun-Mo
authors.initials: HM
authors.lastname: Ryoo
authors.forename: Gwan-Shik
authors.initials: GS
authors.lastname: Kim
authors.forename: Jeong-Hwa
authors.initials: JH
authors.lastname: Baek
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D012886:Skull / Q000166:cytology / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D016328:NF-kappa B; C493716:Runx2 protein, mouse; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; C492381:Smurf1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4