Figure 4. After UVR, cells complemented with APIM-mutated XPA accumulate γH2AX foci at the site of replication.

(A) Normalized γH2AX intensity measured by in-cell western (LI-COR Bioscience) (mean ± SD, n = 4) 24 h after exposure to UV-B. The γH2AX intensity is normalized against the DNA content using Draq5 and the intensity of untreated cells. (B) Images of immunostained cells. The cells were exposed to UV-B 24 h prior to fixation. Lower UVR-dose was applied for the XPA^−/− cells to avoid excessive apoptosis. Bar: 5 µm. (C) Fractions of replication foci (PCNA) colocalizing with γH2AX. Each dot represents one cell, on average 35 foci were counted in each cell (mean ± SEM, n = 5 and 15). The P-value is derived by unpaired t-test. Only cells resembling S phase cells and expressing comparable levels of the YFP constructs were included.