When bound to eIF4E, 4E-BP1 (also known as PHAS-1) inhibits cap-dependent translation. Upon hyperphosphorylation of 4E-BP1 this interaction is disrupted and cap-dependent translation is activated. Both the PI3 kinase/Akt pathway and FRAP/mTOR kinase regulate 4E-BP1 activity. Multiple 4E-BP1 residues are phosphorylated in vivo; while phosphorylation by FRAP/mTOR on Thr37 and Thr46 does not prevent the binding of 4E-BP1 to eIF4E, it is thought to prime 4E-BP1 for subsequent phosphorylation at Ser65 and Thr70.