[RNA transport in the embryonic cell].

The modern data on RNA transport in the cells of early embryos are reviewed. A special attention is paid to the specificity of posttranscriptional mRNA transformation and the control of its transport from the nucleus to the cytoplasm. These processes in the embryonic cell differ from those in the adult one: in the embryos the rate of transport of mRNA molecules in the cytoplasm increases with the development (with the onset of gastrulation); the process of polyadenylation in some mRNA molecules takes place in the cytoplasm rather than in the nucleus; besides, the high molecular weight mRNA fractions are localized in the cytoplasm (in the adult cells they are found only in the nucleus). A study of the mechanisms of control of mRNA transport from the nucleus in the cytoplasm has shown that the now existing concepts on the participation of nucleolus, as well as of translation mechanisms in the control of mRNA transport appear to be true only for the differentiated cells and cannot be used to account for the control of mRNA transport in the embryos. For the embryonic cells the hypothesis on the selection of populations of mRNA molecules at the level of transport for their entry into the cytoplasm holds true. The patterns of RNA transport during the cell division are also considered, with respect to the phenomenon of migration of some RNA populations synthesized prior to the onset of division in the nuclei of daughter cells.