FIGURE 4.

The PTB2 domain is essential for Fe65 to potentiate estrogen stimulation of ERα transcriptional activity. A, HeLa cells were plated and transfected as in Fig. 1A but together with the indicated amounts of HA-tagged Fe65 or PTB2 deletion mutant. Cells were treated with E2, and ERα activity was similarly determined. B, IB analyses were performed in parallel with lysates from transfected cells to show that Fe65 and the PTB2 deletion mutant were expressed at comparable levels and did not change ERα protein expression. β-Actin blot was included to show even loading.