Wild type (E2f1+/+) and E2f1S29A/S29A MEFs were exposed to 250 J/m2 of UVB and ChIP was performed 30 min post-irradiation with the indicated antibodies: (a) E2F1, (b) GCN5, (c) H3K9ac, (d) XPC, (e) XPA, and (f) control IgG. An ELISA was used to measure the amount of CPD in immunoprecipitated DNA. The relative enrichment of CPD in genomic DNA was calculated from two independent samples per group subjected to ELISA in triplicate.