Figure 2.

TGF-β and rapamycin together induce the dephosphorylation of nuclear Rb. The cytoplasmic (C) and nuclear (N) extracts prepared in Fig. 1a were analyzed by immunoblotting with antibodies specific for Rb phosphorylated on Thr⁸²¹ (P-Rb(Thr⁸²¹)), Rb phosphorylated on Ser²⁴⁹/Thr²⁵² (P-Rb(Ser²⁴⁹/Thr²⁵²)), and total Rb. Where two bands of total Rb are apparent, the upper band represents hyperphosphorylated Rb and the lower band hypophosphorylated Rb. Cont., control; T + R, 10 ng/ml TGF-β1 plus 100 nM rapamycin; HMEC, primary human mammary epithelial cells.