Figure 8.
Enhanced DNA repair correlates with high levels of XPC in UV-induced UDS in DKO cells expressing XPC-GFP/hHR23B. (A) Histogram of UV-induced UDS in DKO cells expressing XPC-GFP/hHR23B. Five hours after exposure to 10 J/m2 of UV-C, cells were subsequently irradiated with 16 J/m2 of UV-C and labeled with [3H]thymidine for 1 h (white columns, mean of UDS level is 25 ± S.E.M. 1). In parallel, nonprechallenged cells only exposed to 16 J/m2 of UV-C were used as controls (black columns, mean of UDS level is 16 ± S.E.M. 0.6). Asterisks indicate the mean values of the UDS levels. Incorporation of radioactivity was measured by autoradiography and grain counting (130 fixed squares counted per cell line; each square represented ∼50% of the nucleus surface). UV-induced UDS of wild-type (mean 17 ± S.E.M. 0.8) fibroblasts were measured as a control (data not shown). (B) Effect of microinjection of XPC-GFP cDNA on UV-induced UDS in human wild-type (C5RO) fibroblasts. Shown is a micrograph of a wild-type homodikaryon (numbered 1) microinjected with XPC-GFP in one of the nuclei and subjected to UV-induced UDS. Prior to UDS, fluorescence images were captured (inset in B). The injected cell has a considerably larger number of grains above its nuclei than the noninjected, surrounding mononuclear cells (numbered 2).