Reduced activity and cytoplasmic localization of Runx2 is observed in C3h10t1/2 cells overexpressing Tbx3.

Tbox3, a T-box containing transcription factor, has been reported to negatively regulate osteoblastogenesis. Here, we studied the effects mediated by Tbx3 on the master osteogenic transcription factor Runx2 in C3h10t1/2 cells. Dual-luciferase assay results showed that Tbx3 interferes in the Runx2-mediated activation of osteopontin promoter by abrogating Runx2 activity. Immunofluorescence study demonstrated that Runx2 was simultaneously localized in the nucleus and the cytoplasm of Tbx3-overexpressing cells. The results obtained in this study indicate that Tbx3 abrogates Runx2 activity and elevated expression levels of Tbx3 in the cells can result in mislocalization of Runx2.