FIG. 5.

RANKL activation is regulated by BMP signaling. A schematic presentation of RANKL promoter reporters. The top panel is the long promoter reporter (−7000 to +111 bp) and the bottom panel is the short promoter reporter (−704 to +111 bp) (A). ATDC5 cells were transfected with RANKL promoter plasmids (−704 to +111 and −7000 to +111) and treated with BMP2 (100 ng/ml) for 48 h. A luciferase assay was conducted (B). ATDC5 cells were co-transfected with short-form RANKL promoter plasmids (−704 to +111) and a Smad1 expression vector in the presence or absence of BMP2 (100 ng/ml) for 48 h. A luciferase assay was performed (C), and RANKL mRNA expression was determined by real-time RT-PCR (D). ATDC5 cells were co-transfected with RANKL-Luc, Smurf1, Smad6, and Smad1 and were treated with BMP2. A luciferase assay was performed (E). ^a p < 0.05.