ИСТИНА

Transcriptional regulation of Oct4 gene in mouse development is controlled by three important cis-elements — the proximal promoter (-21-47 bp from TSS), the proximal enhancer (PE, -1101-1122 bp from TSS) and the distal enhancer (DE, -1966-2023 bp from TSS) Each of these elements is the subject to binding of regulatory protein trans-factors and DNA methylation While the PE activates Oct4 expression in epiblast cells, the DE is crucial for Oct4 expression in the inner cell mass, cultured pluripotent cells, and in germ cell precursors Two essential regulatory elements have been found to mediate DE activity — sites 2A and 2B It has been shown in vitro that site 2B is a specifc target for Oct4 and Sox2 heterodimer while trans-acting factors for the site 2A have not been identifed Moreover, whilst site 2B is occupied by factors specifc for pluripotent cells (Oct4 and Sox2), site 2A binds proteins present in both pluripotent and differentiated cells Using the EMSA, afnity chromatography, and mass-spectrometry approaches, we have successfully isolated from the mouse brain extracts several proteins specifcally binding site 2A Mutagenesis of the site 2A allowed us to confrm that protein-DNA interactions in vitro were sequence-specifc Verifcations of the interaction of identifed proteins with site 2A in vivo and their relevance to Oct4 gene transcriptional activity through specifc interaction with the DE in pluripotent stem cells are now in progress The work was supported by the Russian Science Foundation (grant № 14-50-00068).