FIG. 1.

Serial Northwestern and Western blotting of nuclear proteins. Nuclear proteins were isolated from HuH-7 cells and electrophoresed on a sodium dodecyl sulfate-polyacrylamide gel. The separated proteins were transferred to a polyvinylidene difluoride membrane. PRE binding proteins (arrow) were revealed by Northwestern blotting with a ³²P-labeled PRE fragment III probe and autoradiography (right panel). Northwestern blotting is relatively inefficient in detecting the binding of GAPDH to fragment III; hence, the GAPDH band is not visible in the autoradiogram. The blot was washed, and PTB was detected by Western blotting with rabbit antibodies against human PTB (left panel). Numbers at left are kilodaltons.