p70 S6 kinase: an enigma with variations

The S6 ribosomal protein is phosphorylated by p70 S6 kinase (p70S6k). Although the cellular role of S6 phosphorylation is still not fully clear, studies on p70S6k and its activation have revealed the existence of a novel signalling pathway, clues to the mechanism of action of certain immunosuppressants and insights into the control of gene expression at the levels of transcription and translation.