FIG. 3.

Immunoprecipitation of nuclear proteins cross-linked to PRE fragment III. Nuclear proteins extracted from HuH-7 cells were cross-linked by UV irradiation to ³²P-labeled PRE fragment III. After RNase digestion, the mixture was divided into three portions. One was not further manipulated (NO IP), one was immunoprecipitated with rabbit antibodies to human PTB, and one was immunoprecipitated with rabbit antibodies to human integrin αl (Int.). All three portions were then electrophoresed on a sodium dodecyl sulfate-polyacrylamide gel, and the labeled proteins were detected by autoradiography. The band corresponding to PTB is marked with an arrow. A weak, nonspecific band migrating at ∼43 kDa is present in both immunoprecipitates. Numbers at left are kilodaltons.