Cloning and characterization of p70S6Kβ defines a novel family of p70 S6 kinases

The human cDNA encoding a novel protein serine/threonine kinase most closely related to p70 S6 kinase was isolated from the human erythroleukemia cDNA library and termed p70(S6K beta). p70(S6K beta) has, 67% amino acid identity in overall sequence with human p70(S6K), and the potential phosphorylation sites of p70(S6K) are conserved in p70(S6K beta). Northern blot analysis identified two major transcripts of p70(S6K beta) that are ubiquitously expressed in human adult tissues. Similar to p70(S6K), p70(S6K beta) was activated by serum stimulation, and the serum-induced activation was inhibited by wortmannin and rapamycin. These findings suggest that p70(S6K beta) is, isoform of p70(S6K) With Similar regulatory mechanisms, (C) 1998 Academic Press.