Disclosure: All authors state that they have no conflicts of interest.
Original Research Article
Tumor necrosis factor-α enhances the transcription of smad ubiquitination regulatory factor 1 in an activating protein-1- and runx2-dependent manner†
Article first published online: 28 JAN 2013
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Cellular Physiology
Volume 228, Issue 5, pages 1076–1086, May 2013
How to Cite
Lee, H.-L., Yi, T., Baek, K., Kwon, A., Hwang, H. R., Qadir, A. S., Park, H.-J., Woo, K. M., Ryoo, H.-M., Kim, G.-S. and Baek, J.-H. (2013), Tumor necrosis factor-α enhances the transcription of smad ubiquitination regulatory factor 1 in an activating protein-1- and runx2-dependent manner. J. Cell. Physiol., 228: 1076–1086. doi: 10.1002/jcp.24256
- Issue published online: 28 JAN 2013
- Article first published online: 28 JAN 2013
- Accepted manuscript online: 5 OCT 2012 07:49AM EST
- Manuscript Accepted: 27 SEP 2012
- Manuscript Received: 10 MAY 2012
- National Research Foundation of Korea (NRF). Grant Numbers: 2010-0021044, 2011-0016548
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. J. Cell. Physiol. © 2012 Wiley Periodicals, Inc.