[Cyclic nucleotides in the regulation system of cell proliferation and differentiation]

The paper deals with certain aspects in the role of cyclic nucleotides in cell differentiation and proliferation. The content of cyclic nucleotides and activity of protein kinases are determined for the cell cycle stages of a synchronous plasmodium culture of true myxomycete Physarum polycephalum. Studies in the biological role of the brain cAMP-dependent protein kinase show that during phosphorylation of nuclei from the brain and subsequent isolation of chromatin its matrix activity is higher than the control one. When a regulatory subunit is added to the standard RNA-polymerase reaction, the total level of transcription increases for eucaryote RNA-polymerase. The constant of the regulatory subunit binding with chromatin from the brain is 10(10) M-1. Studies in translocation of tritium-labelled cAMP-dependent protein kinase and its subunits to interphase nuclei and in acception of these proteins by metaphase chromosomes in different cell cultures state that sAMP-dependent protein kinase penetrates into the nucleus in the dissociated state. It is established that disturbance of the regulatory subunits translocation into the nucleus and its acception by chromosomes when cell are transformed by SV40 virus is completely restored by adding cAMP. For cells, which suffered the malignant transformation of another type (spontaneous human cancer--KB, HeLa), and essential nuclear translocation and a complete absence of acception by chromosomes for the regulatory subunit are found. An assumption is made that compartmentation of cAMP-dependent protein kinase, in particular of its regulatory subunit, plays an important role in the organism vital activity and disturbances arising in neoplastic transformation are connected with changes in translocation and acception of the regulatory subunit in the nucleus.