Cell-Cycle-Dependent Oscillation of GATA2 Expression in Hematopoietic Cells.

Manipulation of hematopoietic stem cells (HSC) is a key issue in transplantation therapy and regenerative medicine, and methods enhancing proliferation of HSC with keeping pluripotency (self-renewal) are awaited. GATA2 is a transcription factor controlling proliferation with keeping pluripotency of HSC (self-renewal), although simple overexpression experiments of GATA2 do not induce proliferation of HSC. In this study, we showed the cell-cycle dependent oscillation of GATA2 expression, high in S phase but low in G1/S and M phase, in leukemic cells, and also in cord-blood CD34⁺ cells cultured under stimulation of Notch signals. Using green fluorescent protin-GATA2 fusion protein, we demonstrated the cell-cycle specificity of proteasome- dependent degradation of GATA2, which was inhibited by the treatment with Roscovitine, a selective inhibitor of cyclin- dependent kinase (CDK). Immunoprecipitation- immunoblotting analysis demonstrated phosphorylation of GATA2 at CDK-consensus motifs, S₀P₊₁ and T₀P₊₁, and the interaction of cyclin A, Cdk2, and Cdk4 with GATA2. Furthermore, mutants in CDK-consensus phosphorylation motifs exhibited altered expression profiles of GFP fusion proteins. These results indicate cell-cycle dependent control of GATA2 expression through the phosphorylation and interactions with cyclin-CDK systems, suggesting the possible effect of cell-cycle-specific induction of GATA2 expression on the self-renewal of HSC.