Figure 2.

p53 stabilization occurs in Bax−/− cerebellum, whereas Bax protein levels are unaffected by IR. (A) Examination of p53 stabilization by using immunohistochemistry shows equivalent p53 stabilization in the EGL of WT and Bax−/− cerebellum after IR but reduced stabilization in Atm−/− and an absence in p53−/− tissue. (×200.) (B) Bax levels do not alter up to 5 hr after IR. After identification of p53, the immunoblot was reprobed with an antibody to Bax; 1–4 are P5 cerebellum samples 0, 0.5, 1, and 5 hr after IR, respectively. (C) p53 is induced in WT and Bax−/− eye after IR (lanes 5 and 8, respectively), whereas induction is reduced in Atm−/− and absent from p53−/− tissue (lanes 6 and 7, respectively). The induction of p53 in the Atm−/− retina occurs in multipotential cells of the periphery, where IR-induced apoptosis is independent of Atm (4). Bax levels are similar in WT, Atm−/−, and in p53−/− cerebellum and eye (1–3, respectively) and are not obviously affected by IR (WT; Atm and p53 are 5, 6, and 7, respectively). Bax−/− tissues (4 and 8) have no detectable Bax. Lanes 1–4 and 5–8 are extracts from unirradiated or irradiated animals, respectively. Control is a region of the Ponceau S-stained membrane used for the anti-Bax immunoblot of the cerebellum to illustrate protein loading and transfer.