Protein Extraction and Western Blot Analysis

Total protein extractions were performed as previously described [59 (link)] Nuclear/cytoplasmic protein fractionations were performed using the NE-PER Nuclear and Cytoplasmic Extraction Reagents (Thermo, Waltham, MA, USA), according to manufacturer's instructions. Histone extraction [60 (link)] and immunopreciptiation [59 (link)] experiments were performed as previously described. Western blot analyses were performed according to standard protocols. Antibodies used were anti-ATM S1981p (Rockland, Philadelphia, PA, USA), anti-p53 DO-1, anti-p-p53 (Ser15), anti-ATM 2C1 (Santa Cruz), anti-RanBP9 (Abcam, Cambridge, MA, USA), anti-pChk2 (Thr68), anti-Chk2, anti-γH2AX, anti-H2A, anti-PARP, anti-GAPDH-HRP-conjugated, anti-β-actin (Cell Signaling Technology, Danvers, MA, USA) and anti-p84 (GeneTex, San Antonio, TX, USA). ImageQuant software (Biorad, Hercules, CA, USA) was used for the quantification of western blot data.