Biopolym. Cell. 2005; 21(3):293-295.
Identification of endogeneous isoform of ribosomal protein S6 kinase - S6K2
- Institute of Molecular Biology and Genetics, NAS of Ukraine
150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03680
- University College London
Gower Str., London WC1E 6BT, UK
S6K1 and S6K2 belong to the family of ribosomal protein S6 kinases. S6K1 has two isoforms - cytoplasmic (S6K1/II, 70 kDa) and nuclear (S6K1/I, 85 kDa) possessing nuclear localization signal within the N-terminal extension region. It is believed that S6K1 isoforms are generated from a single gene by alternative mRNA splicing or the use of alternative translational start sites. S6K1/II is implicated in ribosomal biogenesis via regulation of ribosomal proteins mRNAs translation. The function of S6K1/I is not clear. The high level of structural homology between S6K1 and S6K2 suggest that S6K2 has two isoforms as well, but Western blot analysis of cell lysates and tissue homogenates does not reveal S6K2/1 with expecting molecular mass (~70 kDa). However, 105 kDa protein has been detected by anti-S6K2 polyclonal antibodies.
Keywords: S6K1, S6K2, ribosomal protein S6
 Avruch J, Belham C, Weng Q, Hara K, Yonezawa K. The p70 S6 kinase integrates nutrient and growth signals to control translational capacity. Prog Mol Subcell Biol. 2001;26:115-54.
 Dufner A, Thomas G. Ribosomal S6 kinase signaling and the control of translation. Exp Cell Res. 1999;253(1):100-9.
 Price DJ, Nemenoff RA, Avruch J. Purification of a hepatic S6 kinase from cycloheximide-treated Rats. J Biol Chem. 1989;264(23):13825-33.
 Gout I, Minami T, Hara K, Tsujishita Y, Filonenko V, Waterfield MD, Yonezawa K. Molecular cloning and characterization of a novel p70 S6 kinase, p70 S6 kinase beta containing a proline-rich region. J Biol Chem. 1998;273(46):30061-4.
 Richardson CJ, Schalm SS, Blenis J. PI3-kinase and TOR: PIKTORing cell growth. Semin Cell Dev Biol. 2004;15(2):147-59.
 Valovka T, Filonenko V, Palchevsky S, Velikiy M, Drobot L, Waterfield M, Matsuka G, Gout I. Functional and regulatory properties of p70S6 kinase ?. Biopolym Cell. 1999; 15(5):415-21.
 Valovka T, Verdier F, Cramer R, Zhyvoloup A, Fenton T, Rebholz H, Wang ML, Gzhegotsky M, Lutsyk A, Matsuka G, Filonenko V, Wang L, Proud CG, Parker PJ, Gout IT. Protein kinase C phosphorylates ribosomal protein S6 kinase betaII and regulates its subcellular localization. Mol Cell Biol. 2003;23(3):852-63.
 de Groot RP, Ballou LM, Sassone-Corsi P. Positive regulation of the cAMP-responsive activator CREM by the p70 S6 kinase: an alternative route to mitogen-induced gene expression. Cell. 1994;79(1):81-91.
 Koh H, Jee K, Lee B, Kim J, Kim D, Yun YH, Kim JW, Choi HS, Chung J. Cloning and characterization of a nuclear S6 kinase, S6 kinase-related kinase (SRK); a novel nuclear target of Akt. Oncogene. 1999;18(36):5115-9.
 Minami T, Hara K, Oshiro N, Ueoku S, Yoshino K, Tokunaga C, Shirai Y, Saito N, Gout I, Yonezawa K. Distinct regulatory mechanism for p70 S6 kinase beta from that for p70 S6 kinase alpha. Genes Cells. 2001;6(11):1003-15.
 Savinska LO, Kijamova RG, Pogrebnoy PV, Ovtsharenko GV, Gout IT, Filonenko VV. Comparative characterization of S6 kinase ? and ? isoforms expression in mammalian tissues. Biopolym Cell. 2001; 17(5):374-9.
 Pogrebnoy PV, Kukharenko AP, Tykhonkova IA, Pal'chevskiy SS, Savinskaya LA, Pogrebnaya AP, Valevka TI, Markeeva NV, Soldatkina MA, Matsuka GKh, Gout IT, Filonenko VV. Generation and characterization of monoclonal antibodies to p70S6kinase. Exp. Oncol 1999; 21(4):232вЂ“8.