FIG. 3.

TAT-p16^INK4A prevents T lymphocytes from entering the cell cycle and increasing in size. Nonactivated T cells were transduced with TAT-p16^INK4A or TAT-p16^MUT and stimulated for 48 h with PMA-ionomycin (PMA/Iono). Similarly, roscovitine at the concentrations shown was added, and the cells were stimulated with PMA-ionomycin or CD3/CD28. (A) Total cell protein (stained with FITC) and DNA (stained with PI) were quantified by flow cytometry. (B) Forward scatter was used as a measure of cell size. (C and D) Inhibition of cell cycle progression by roscovitine. T cells were stimulated with CD3/CD28, and 20 μM roscovitine was added at 0 or 24 h. Samples were taken at 48 h and assayed for cell cycle progression and the percentages of the cells in G₀, G₁, and S+G₂/M are indicated in panel C. pRb phosphorylation and induction of proteins associated with cell cycle entry were also analyzed in samples from the same experiment (shown in panel D). The data are representative of six (A and B) and two (C and D) separate experiments, respectively.