Figure 4. GSNOR induction by hydrogen peroxide involves p53 as downstream effector of ATM/CHK2 phosphorylation axis.

• A
  HEK293 cells were treated for 24 h with 100 μM H₂O₂ in the presence or absence of 20 μM pifithrin‐α (Pft). Basal and phospho‐active forms of ATM, CHK2, p53, and GSNOR were assessed by Western blot. Phospho:basal level ratios of ATM, CHK2, and p53 (normalized to Vinculin), along with densitometry of GSNOR immunoreactive bands (normalized to GAPDH) are expressed as arbitrary units. Values shown represent the means ± SD of n = 3 independent experiments. *P < 0.05; **P < 0.01; n.s., not significant.
• B
  HEK293 cells were transfected with a pool of siRNA against p53 (sip53) or with control siRNA (siScr) for 24 h and treated for additional 24 h with 100 μM H₂O₂. Basal and phospho‐active forms of ATM and CHK2, as well as p53 and GSNOR, were assessed by Western blot. Phospho:basal level ratios of ATM and CHK2 (normalized to Vinculin), along with densitometry of GSNOR immunoreactive bands (normalized to GAPDH) are expressed as arbitrary units. Values shown represent the means ± SD of n = 3 independent experiments. *P < 0.05; **P < 0.01; n.s., not significant.
• C
  HCT116 cells expressing the wild‐type form of p53 (p53^wt), or an empty vector (Empty, selected as negative control), were treated for 24 h with 100 μM H₂O₂. Basal and phospho‐active forms of ATM and CHK2, p53, and GSNOR were assessed by Western blot. Vinculin and GAPDH were used as loading controls. Phospho:basal level ratios of ATM and CHK2, along with densitometry of p53 and GSNOR immunoreactive bands are expressed as arbitrary units. Values shown represent the means ± SD of n = 3 independent experiments. *P < 0.05; **P < 0.01; n.s., not significant.

Source data are available online for this figure.