FIGURE 4.
SPE B induces phosphorylated STAT1 translocation to the nucleus. Cells (2 × 105) were treated with SPE B (20 μg/ml) for the indicated times or PBS for 2 h. The cytoplasmic (A) and nuclear (B) extracts were immunoblotted using anti-STAT1 antibody. β-Actin and proliferating cell nuclear antigen (PCNA) were internal controls for cytoplasmic and nuclear extracts, respectively. Cells were also preincubated with AG490 (15 μm) for 1 h and then treated with SPE B or G308S (20 μg/ml) for 2 h. The phosphorylation of STAT1 on tyrosine 701 in nuclear extracts was determined (C).