Figure 1.

(A) TGF-β rapidly induces Smad7 mRNA levels. Poly(A)⁺ RNA (4 μg) from HaCaT cells that were untreated or treated with TGF-β for different lengths of time was analyzed by Northern blot assay by using the N-terminal domain of Smad7 as a probe. (B) TGF-β can increase the stability of Smad7 RNA. Poly(A)⁺ RNA (4 μg) from HaCaT cells that were treated with actinomycin D (1 μg/ml) in the absence or presence of TGF-β (500 pM) for various times was analyzed by Northern blot analysis with the Smad7 probe. In both A and B, each blot was subsequently hybridized with a glyceraldehyde-3-phosphate dehydrogenase probe to normalize the amount of RNA loaded.