(A–B) U2OS Peli1 inducible stable line cells were transfected with control siRNA or siRNA against p53 or Mdmx. After 24 hours, the cells were without treatment or treated with 0.1 μg/ml of doxycycline 48 hours. (A) Western blot analysis of cell extracts with antibody against Peli1, Mdm2, Mdmx, p53, p21 and β-actin. (B) p21 and Mdm2 mRNA levels were determined by real-time PCR in these cells. (C) Western blot analysis of cell extracts from two U2OS Peli1 CRISPR-Cas9 knock-out cell lines (CRISPR 1 and 2) with antibody against Mdm2, Mdmx, p53, Peli1, p21 and β-actin. Parental U2OS cells were used as the control. (D) p21 and Mdm2 mRNA levels were determined by real-time PCR in U2OS Peli1 knock-out cell lines. Parental U2OS cells were used as the control.