FIG. 3.

Atm deficiency does not affect p53 transactivation function in CP. Representative in situ RNA hybridization signals are shown for p21 (A, C, and E) and bax (B, D, and F) expression. p21 RNA is readily detectable in TgT₁₂₁ (A) as well as in TgT₁₂₁ Atm^−/− (C) CP. bax RNA levels are also equally expressed in TgT₁₂₁ (B) and TgT₁₂₁ Atm^−/− (D) cells. bax and p21 expression in TgT₁₂₁ CP are both p53 dependent, as seen in TgT₁₂₁ p53^−/− cells (E and F). (G) Quantitative comparisons of RNA levels; signals in TgT₁₂₁ are designated as 100%. The signal detected in CP by using a bax or p21 sense probe was at about the background level, ensuring the specificity of the assay. Ten fields of each sample were analyzed. Standard errors in each field are less than 10% of the relative mean value.