FIG. 5.
p16INK4A inhibits DNA synthesis and cell proliferation in v-Jun-transformed CEFs. (a) v-Jun-transformed CEFs cultured in GM or LS medium were microinjected with control or expression plasmid encoding human p16INK4A together with a plasmid encoding GFP to identify injected cells. After time was allowed for expression, the percentage of injected cells which synthesized DNA in 24 h was determined by BrdU labeling and immunocytochemistry. At least 100 surviving injected cells were analyzed in each case. The experiment was repeated three times with similar results. (b) CEFs doubly infected with the indicated combinations of retroviruses were seeded at two dilutions (105 or 106 cells/dish) and selected with G418 for 5 days after being plated. The cultures were fixed in ethanol and stained with Giemsa stain to visualize colony growth.