Fig. 1. UVA irradiation induces hOGG1 relocalisation to foci associated to the nuclear matrix. (A) A HeLa cell line expressing hOGG1-GFP was UVA (UVA) or mock (NI) irradiated and allowed to recover for 2 hours. Cells were then either directly fixed (-CSK) or pre-extracted with detergent-containing buffer (+CSK) before fixation. DNA was stained with DAPI. UVA-treated cells were further treated with DNase (absence of DAPI staining indicating the complete degradation of DNA) or RNase. (B) NI and UVA-irradiated cells were separated into fractions S1 (soluble proteins), P1 (proteins bound to DNA) and P2 (nuclear matrix proteins). Samples were analysed by western blot with anti-hOGG1 antibodies, detecting the fusion protein (upper panel) and, after overexposure, the endogenous hOGG1 (bottom panel). Middle panel shows the nuclear matrix protein Sm. (C) UVA-irradiated cells were allowed to recover for the indicated times. Soluble proteins were extracted with CSK buffer before fixation and DAPI staining. (D) Kinetics of hOGG1 accumulation in the P2 fraction after UVA irradiation. (E) UVA-irradiated cells were incubated at 37°C for 2 hours, and BrdU was added to the medium for the last 45 minutes. BrdU was visualised using an anti-BrdU antibody (red). Bars, 4 µm.