Figure 2.

PTEN/MMAC1 blocks phosphorylation of the translation repressor 4E-BP1, a downstream target of the PI3-kinase/Akt pathway. (A) 293T cells were transfected with 4E-BP1 in the presence or absence of wild-type PTEN/MMAC1 and either Myr-Akt or constitutively active PI3-kinase then starved of serum for 48 hr. Phosphorylation of 4E-BP1 was monitored by altered electrophoretic mobility in immunoblot assays of whole-cell lysates using an anti-HA antibody. Expression of PTEN/MMAC1, PI3-kinase, and Myr-Akt was monitored by immunoblot using anti-PTEN antibody, anti-Myc antibody, and anti-HA antibody respectively. (B) 293T cells were transfected with 4E-BP1 in conjunction with plasmids noted at the top of each lane. Phosphorylation of 4E-BP-1 was monitored as described in B.