Abstract
YB-1 is a eukaryotic protein with numerous intra- and extracellular functions based on its ability to interact with RNA, DNA, and many proteins. In spite of achievements in studying its functions, regulation of YB-1 synthesis in the cell remains poorly understood. In the current study Western and Northern blotting were used to determine the amounts of YB-1 and YB-1 mRNA in rabbit organs and several cell lines. As found, in the majority of studied eukaryotic cells a considerable proportion of YB-1 mRNA was stored in free mRNPs, i.e., was poorly translated. Also, we demonstrated that YB-1 synthesis depended on conditions that determined the rate of cell division. Specific suppression of YB-1 synthesis resulted from inhibition of the mTOR signaling pathway with inhibitor PP242, but not rapamycin. Experiments on reporter constructs showed that dependence of YB-1 mRNA translation on activity of the mTOR signaling pathway was dictated by 5′ untranslated regions of this mRNA, irrelatively of the TOP-like sequences at the beginning of 5′ UTR.
Highlights
YB-1 belongs to proteins with a cold shock domain and performs many functions in the cell
Prior to determining the level of YB-1 mRNA translation, we estimated the amounts of YB-1 and YB-1 mRNA in several eukaryotic cell cultures and various rabbit organs
The only exception is amounts of YB-1 mRNA and YB-1 detected in 3T3 cells, where YB-1 mRNA exceeds the level typical of other cell lines, while the amount of YB-1 does not approach it
Summary
YB-1 belongs to proteins with a cold shock domain and performs many functions in the cell (reviewed in [1]). By binding to nucleic acids, YB-1 regulates virtually all DNA- and mRNAdependent events in eukaryotic cells, including replication and reparation of DNA [3,4,5], as well as transcription [1], splicing of mRNA [6,7] and mRNA translation [8,9,10,11]. In other words, it performs both overall and specific regulation of gene expression at differential levels. Its elevated concentration in the cytoplasm may prevent oncogenic transformation of the cell caused by activated PI3K/Akt kinase signaling pathway [17]
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