Ribosomal protein S6 is a component of the 40S ribosomal subunit and is therefore thought to be involved in regulating translation. Once thought to regulate the translation of 5' terminal oligopyrimidine (TOP) RNA, this has since been disproven. While the true function of rpS6 is currently under investigation, studies have shown that it is involved in the regulation of cell size, cell proliferation, and glucose homeostasis.

Studies show that the p70 ribosomal protein S6 kinases (S6K1 and S6K2) and p90 ribsomal protein S6 kinases (RSK) both phosphorylate rpS6 and that S6K1 and S6K2 predominate this function.