Recruitment of GFP-UBF1, HP1β, γH2AX, and 53BP1 to UVA-induced DNA lesions. (A) Cells transiently expressing GFP-UBF1 were microirradiated using a 355-nm UVA laser. Recombinant GFP-UBF1 (green) in (Aa) immortalized mouse embryonic fibroblasts and (Ab) primary mouse embryonic fibroblasts was monitored after local microirradiation by a 355-nm UVA laser. Magnification of the irradiated nucleus is shown. (B) Endogenous UBF1/2 (red) was analyzed by immunofluorescence after local UVA microirradiation of regions of interest (yellow) in 3T3 cells stably expressing GFP-HP1β (green). Irradiated cells were fixed in 4% formaldehyde and stained with appropriate antibodies against (C) HP1β (red), (D) γH2AX (red), and (E) 53BP1 (red). Regions of interest (yellow) were irradiated by a 355-nm UVA laser. Cell nuclei were visualized by DAPI (blue), and UBF1 was tagged by GFP (green). For each event, 10 nuclei were analyzed in three independent experiments. IF, immunofluorescence; LCI, live-cell image; Nu, nucleolus.