Enforced expression of

CUL-4A promotes proliferation and reduces exit from the cell cycle after induction of granulocytic differentiation.(A) The cell lines overexpressing CUL-4A and control cell lines were grown in the presence or absence of 0.5% DMF for 0 to 6 days, and the numbers of viable cells were counted. The averages of 5 independent experiments are shown for the DMF-induced cells (open symbols) and the averages of 3 independent experiments are shown for uninduced cells (solid symbols). Symbols are as follows: untransfected PLB-985 cells, diamond; empty vector control, square;CUL-4A-HA1, circle; CUL-4A-HA2, triangle. Error bars denote SEM. Only a small difference in the proliferation of untransfected and empty vector control cells was observed. (B) The cell lines overexpressing CUL-4A and control cells were induced to differentiate with DMF for 4 days. Before DMF was added and after 4 days of induction, cells were removed, DNA content was determined by propidium iodide staining and flow cytometry, and the relative number of cells in each phase of the cell cycle was determined. Error bars represent SEM. Results representative of 3 independent experiments are shown.