Fig. 1. TGF-β inhibits the expression of cbfa1 mRNA independently of new protein synthesis. The cbfa1 mRNA, visualized following northern blot hybridization and autoradiography, is shown. (A) Primary mouse calvarial osteoblasts cultured for 48 h in differentiation medium in the presence of TGF-β (5 ng/ml) express reduced levels of cbfa1 mRNA. (B) Treatment with TGF-β for 8 h decreases the level of cbfa1 mRNA in ROS 17/2.8 cells. (C) TGF-β treatment of caIB 2T3 cells during the 12 h period in differentiation medium represses cbfa1 mRNA expression. (D) ROS 17/2.8 cells were treated with TGF-β for 8 h as in (B) in the absence or presence of cycloheximide (CHX) (10 µg/ml) or with cycloheximide alone. Ethidium bromide-stained gels are included to show similar loading of RNA.