Immunoblotting and Immunofluorescence of DNA Repair Proteins

Whole cell extracts were prepared from HNSCC cells and analysed by immunoblotting as previously described (9 (link)). RAD51 antibodies were from Bethyl Laboratories (Montgomery, USA), ATR antibodies were from Abcam (Cambridge, UK), CHK1 antibodies were from Cell Signalling Technology (Leiden, The Netherlands), and actin antibodies were from Merck-Sigma (Gillingham, UK). For immunofluorescent staining of RAD51, cells were grown on 13-mm coverslips, unirradiated or irradiated with 4 Gy x-rays, and allowed to repair for 4 h in 5% CO₂ at 37°C, prior to fixing and staining as previously described (9 (link)).