Biopolymers and cell. 2005; 21 (3): 293 - 295

Identification of endogeneous isoform of ribosomal protein S6 kinase - S6K2

G. G. Panasyuk, I. O. Nemazanyy, I. T. Gout, V. V. Filonenko

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.

Key words: S6K1, S6K2, ribosomal protein S6.