| Thus , we termed this Akt specific binding protein APE ( Akt phosphorylation enhancer ) . ^^^ Since APE induced phosphorylation of PKB did not occur in cells treated with wortmannin or LY 294002 , APE itself is not a kinase but seems to enhance or prolong the phosphoinositide 3 kinase dependent phosphorylation of PKB . ^^^ In cells in which APE was suppressed by small interfering RNA , DNA synthesis was significantly reduced with suppression of PKB phosphorylation , suggesting a synergistic role of APE in PKB induced proliferation . ^^^ On the other hand , in cells overexpressing both PKB and APE , despite markedly increased basal phosphorylation of PKB , both DNA rereplication and subsequent Chk 2 phosphorylation and apoptosis were seen , suggesting the involvement of APE in the regulation of cell cycling replication licensing . ^^^ Taking these observations together , APE appears to be a novel regulator of PKB phosphorylation . ^^^ |