Fig. 8. p21 recruitment to DNA-damage sites depends on DNA repair activity. LF1 and XP20PV (XPA) fibroblasts were exposed to local UV-C irradiation (15 J/m2) through filters with 3 µm pores, extracted in situ, and fixed at the indicated times for determination of chromatin-bound PCNA and p21. Samples were immunostained with anti-PCNA polyclonal, and anti-p21 monoclonal antibody, detected respectively with secondary antibody conjugated with Alexa Fluor 488 (green fluorescence) or Alexa Fluor 594 (red fluorescence); DNA was counterstained with Hoechst 33258 (blue fluorescence). Bar, 10 µm.