70 kDa ribosomal protein S6 kinase 1 (p70-S6K) acts to integrate nutrient and growth factor signals in regulation of protein synthesis, cell proliferation, cell growth, cell cycle progression and cell survival. P70-S6K is a downstream effector of the mTOR signaling pathway. P70-S6K phosphorylates specifically ribosomal protein S6 in response to insulin or several classes of mitogens. During translation initiation, the inactive form associatess with the eIF-3 comple, Xenopus/Amphibian, under conditions of nutrient depletion. Mitogenic stimulation leads to phosphorylation and dissociation from the eIF-3 comple, Xenopus/Amphibian, and the free activated form can phosphorylate other translational targets including EIF4B.