Biopolym. Cell. 2019; 35(2):99-106.
Structure and Function of Biopolymers
Identification of a novel S6K1 splice variant coding for the p60-S6K1 isoform
1Zaiets I. V., 1Holiar V. V., 1Filonenko V. V.
  1. Institute of Molecular Biology and Genetics, NAS of Ukraine
    150, Akademika Zabolotnoho Str., Kyiv, Ukraine, 03143


Aim. To identify a splicing mRNA of S6K1 kinase specific for the p60-S6K1 isoform alone. Methods. RT-PCR, DNA sequencing, Western blotting. Results. RT-PCR analysis of total RNA extracted from MCF-7 cells and subsequent DNA sequencing revealed a novel S6K1 splice variant that possesses additional exon 1a and encodes the p60 isoform of S6K1 only. Moreover, RT-PCR and western blotting were applied to estimate the expression levels of the p60-S6K1 mRNA and protein. A heterogeneous expression of the p60-S6K1 transcript was observed; it did not correlate with the total S6K1 mRNA expression and with the protein content of p60-S6K1 in the studied cell lines. Conclusions. We provide the evidence for the existence of a novel S6K1 splice variant coding for the p60-S6K1 isoform. The cell can employ two distinct pathways of the p60-S6K1 expression based on alternative translation of mRNA common for the main S6K1 isoforms mRNA and/or translation of the novel p60-S6K1 specific mRNA. Since the levels of the p60-S6K1 transcript expression do not correlate with the expression of total S6K1 mRNA, it is plausible that the p60-S6K1 isoform plays a role distinct from that of other isoforms in cellular physiology, as well as in the development of S6K1-related pathologies.
Keywords: p60-S6K1 transcript, alternative splicing, gene expression


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