Fig. 3. IR-induced HMGB2 downregulation is mediated by the ATM-p53-p21 signaling cascade.

(A) CCD18-Lu cells were transfected with siRNAs to knockdown p53 or p21, and exposed to IR. Sixteen hours after exposure, total RNA was prepared, and expression of HMGB2, p21, or p53 was examined by qRT-PCR. (B) H1299 and HT-29 cells harboring a Tet-inducible p21 expression system were treated with doxycycline, and qRT-PCR analysis was performed. (C) Western blot analysis was performed to verify protein levels. (D) ATM knockout A549 cells were established using the CRISPR-CAS9 system. A549 cells with different ATM background levels were treated with 10 Gy IR, and western blot analyses were performed.