RANK IVVY535–538 motif renders osteoclast genes responsive to TNF. A, BMMs expressing GFP, Ch1, or Ch2 were treated with M-CSF (M, 44 ng/ml) alone, M-CSF (44 ng/ml) and Fas-AB (F, 100 ng/ml), or M-CSF (44 ng/ml) and TNF (T, 5 ng/ml) for 18 h. B, BMMs expressing GFP, Ch1, or Ch2 were treated with M-CSF (44 ng/ml) and Fas-AB (100 ng/ml) for 18 h, and the cultures were then continued with M-CSF (44 ng/ml) alone or M-CSF (44 ng/ml) and TNF (5 ng/ml) for 4 days (d). Infected BMMs treated with M-CSF (44 ng/ml) plus Fas-AB (100 ng/ml) or M-CSF (44 ng/ml) plus TNF (5 ng/ml) for 5 days served as positive and negative controls, respectively. Gene expression in A and B was determined by semi-quantitative RT-PCR.