Mechanism of PI 3-kinase regulation by p27^Kip1 protein expression in human erythroid progenitors.

In human erythroid progenitors, PI 3-kinase regulates p27^Kip1 protein expression via proteasome degradation by the E3 ligase SCF^SKP2. (A) D7 + 1 human erythroid progenitors were cultured in serum-free medium for 24 hours in the absence or presence of 2 U/mL Epo and in the absence or presence of LY294002 at 50 μM. Lysates were prepared and analyzed by Western blot with the use of anti–cyclin D1, anti–cyclin D3, anti-Cdk2, anti-p27^Kip1, anti-SCF^SKP2, and antitubulin antibodies. (B) D7 + 1 progenitors were cultured in the presence of 2 U/mL Epo without or with LLnL at 50 μM. Cell lysates were analyzed at indicated times with anti-p27^Kip1, anti-SCF^SKP2, and antitubulin antibodies.