Fig. 2. UV-induced H2AX phosphorylation in quiescent cells occurs at damaged DNA sites and correlates with repair kinetics of UV lesions. (A,B) Growth-arrested MSU-2 cells were locally irradiated with 100 J/m² UV through an isopore membrane filter and incubated for various periods. Cells were fixed and stained with anti--H2AX and anti-CPD antibodies (A), or anti-6-4PP antibody alone (B). (C) MSU-2 cells growing asynchronously (closed symbols) or growth-arrested (open symbols) were irradiated with 10 J/m² UV and incubated for the indicated periods. Genomic DNA was isolated and the amounts of CPD and 6-4PP were determined using an enzyme-linked immunosorbent assay. Each point represents the mean of three experiments and bars indicate the s.d.