FIG. 4.
p19Arf is expressed normally in p16Ink4a null transformants. Lysates were prepared from different cell populations and analyzed by Western blotting using anti-p19Arf and anti-β-actin antibodies. (A) Analysis of lysates from p16Ink4a−/− and a control p16Ink4a+/+ primary transformant prepared 8 days post-explant from agar, near the onset of crisis. (B) Analysis of lysates from p16Ink4a−/− and p16Ink4a+/+ transformants prepared at the end of the crisis period. In both panels, an established cell line expressing abundant p19Arf (+) and an established cell line from a p19Arf null animal (−) are included as controls. The experiments shown are representative of analyses of 14 null and 6 wild-type transformants at crisis onset and 17 null and 15 wild-type transformants at the end of crisis. α-p19Arf, anti-p19Arf antibody; α-β-actin, anti-β-actin antibody.