(A) Though TGF-β induces activity of the synthetic Smad3 reporter gene 3TP-Luc transiently transfected with pRK5 in ATDC5 cells, it represses Runx2-inducible p6OSE2-Luc activity, even more with cotransfected pRK5-Smad3 (B). The activity of -370-MMP-13-Luc is increased by co-transfection of Runx2, but decreased with TGF-β addition or with cotransfected Smad3 or constitutively active TβRI (C). Runx2-knockdown was sufficient to nearly abolish both the rapid 8 h repression (D, F) and delayed 24 h induction (E, G) of MMP-13 mRNA (D, E) and protein (F, G) by TGF-β (5 ng/ml). (*p < 0.05, **p < 0.001 relative to the vehicle-treated controls in A, C, E, and F, and relative to the scramble siRNA in D.)