Time course of nuclear translocation of phospho-Smad3 and phospho-Smad2 induced by PMA/TGF-β treatment. An equal amount of nuclear lysates (30 μg) from RL and DB cells treated with PMA/TGF-β for the time points indicated were analyzed by Western blot analysis. The membranes were probed and reprobed after stripping with different antisera as indicated above.