Cloning and characterization of p70(S6K beta) defines a novel family of p70 S6 kinases.
Saitoh M
et al.
Biochem Biophys Res Commun 1998 Dec;253(2)470-476
Saitoh M, ten Dijke P, Miyazono K, Ichijo H.
Biochem Biophys Res Commun 1998 Dec;253(2)470-476
Abstract: 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(S6Kbeta). p70(S6Kbeta) has 67% amino acid identity in overall sequence with human p70(S6K), and the potential phosphorylation sites of p70(S6K) are conserved in p70(S6Kbeta). Northern blot analysis identified two major transcripts of p70(S6Kbeta) that are ubiquitously expressed in human adult tissues. Similar to p70(S6K), p70(S6Kbeta) was activated by serum stimulation, and the serum-induced activation was inhibited by wortmannin and rapamycin. These findings suggest that p70(S6Kbeta) is an isoform of p70(S6K) with similar regulatory mechanisms.
Molecular cloning and characterization of a novel p70 S6 kinase, p70 S6 kinase beta containing a proline-rich region.
Gout I
et al.
J Biol Chem 1998 Nov;273(46)30061-30064
Gout I, Minami T, Hara K, Tsujishita Y, Filonenko V, Waterfield MD, Yonezawa K.
J Biol Chem 1998 Nov;273(46)30061-30064
Abstract: A novel ribosomal S6 kinase, termed p70 S6 kinase beta (p70beta), which has a highly conserved amino acid sequence compared with that of p70/p85 S6 kinase (p70alpha) within the catalytic, kinase extension, and autoinhibitory pseudosubstrate domains, was identified. However, the amino acid sequence of p70beta differs from that of p70alpha in the noncatalytic amino-terminal region and in the carboxyl-terminal tail, which contains a proline-rich region. The majority of the regulatory phosphorylation sites identified in p70alpha are conserved in p70beta. Two isoforms of p70beta, referred to as beta1 (495 amino acids) and beta2 (482 amino acids), could be expressed from the single gene either by alternative mRNA splicing or by the use of alternative start codons. Here we report the characterization of p70beta2. Similarly to p70alpha, the catalytic activity of p70beta toward ribosomal protein S6 could be rapidly activated by serum, insulin, and phorbol ester in transiently transfected cells. The p70beta kinase was found to be significantly less sensitive to wortmannin and rapamycin than p70alpha. These results indicate that p70beta has the potential to participate in the regulation of protein synthesis and the cell cycle.
