Fig. 4. Induction of p21 expression does not inhibit recruitment of PCNA and DNA repair proteins. LF1 fibroblasts were treated for 16 hours with TSA to induce expression of p21, as described in the Materials and Methods. 30 minutes after exposure to UV-C radiation (10 J/m²), cells were directly lysed in loading buffer, for determination by western blot of total cellular content (total) of p21, PCNA, pol (p125 subunit) and Lig I. (A). Parallel samples were fractionated for western blot analysis of proteins in the chromatin-bound fraction (B). Actin was also determined as a loading control.