Overview:

p70S6K is responsible for the phosphorylation of 40S ribosomal protein S6 and is ubiquitously expressed in human adult tissues (1). p70S6K is activated by serum stimulation and this activation is inhibited by wortmannin and rapamycin. p70S6K activity undergoes changes in the cell cycle and increases 20-fold in G1 cells released from G0 (2). p70S6K activation requires sequential phosphorylations at proline-directed residues in the putative autoinhibitory pseudosubstrate domain, as well as threonine 389 a site phosphorylated by phosphoinositide-dependent kinase 1 (PDK-1).

References:

1.Ferrari, S. et al: S6 phosphorylation and the p70s6k/p85s6k. Crit Rev Biochem Mol Biol. Review. 1994;29(6):385-413. 2.Edelmann, HM. Et al: Cell cycle regulation of p70 S6 kinase and p42/p44 mitogen-activated protein kinases in Swiss mouse 3T3 fibroblasts. J Biol Chem. 1996 Jan 12;271(2):963-71.