Effect of p19-overexpression on cell proliferation and viability. (A) The indicated cells were plated (1 × 105/mL) in growth medium containing IL-3 and incubated with or without zinc. Cell numbers were determined in triplicate cultures of parental 32D cells and cells transfected with the empty vector, as well as the means and standard errors of cell counts of the six clones with zinc-inducible p19. Symbols are: (□), parental 32D cells; (▴), cells transfected with empty vector (no zinc treatment); (▵), cells transfected with empty vector (plus zinc); (•), cells transfected with p19-inducible vector (no zinc); and (○); cells transfected with p19-inducible vector (plus zinc). (B) Cells grown in IL-3 were shifted to medium lacking growth factors and zinc or containing zinc alone. The number of viable cells remaining in the cultures was determined daily by enumerating cells that excluded trypan blue vital dye. Symbols are the same as in (A). (C) Clone 2C cells growing in medium containing IL-3 were treated with zinc for the indicated times, stained with propidium iodide, and their DNA content was determined. The percentage of cells in different phases of the cell cycle was calculated and is given in the upper right of each panel.
