[The DDX5 protein is involved in cell proliferation and differentiation]

The expression of DDX5 protein (RNA-helicase p68) correlates with processes of proliferation and differentiation. However there is no direct evidence of involvement of the protein in these processes. In present work, we studied the influence of DDX5 protein inactivation by si-RNA on the proliferation of Jurkat cells and dynamic of DDX5 expression during differentiation of U-937 cells induced by phorbol 12-myristate-13-acetate (PMA). We showed that the content of DDX5 in Jurkat cells is less in phases G0/G1 as compare to phases G2/M. The treatment of cells with the antisense LV-shDDX5 was followed by the increase of G0/G1 cells. It was also shown that the increase of expression of the DDX5 protein occurred during the initial stages of differentiation, and the peak of expression was registered during the first 2-3 hours after the induction of the cells, later the DDX5 content decreases. The increase of the number of macrophage surface marker CR3 on the membrane of cells occurred only in 24 hours after induction of the cells by PMA. Thus, these data confirm that: (1) the DDX5 protein is essential for normal cell proliferation; (2) the transition from G1 to S/G2 phase is accompanied by an increase of DDX5 protein concentration in the cells; (3) the concentration of the DDX5 protein increases on early stages of U-937 cells differentiation and after decreases.