Fig. 3

Changes in chromatin structure induced by chemical treatment or irradiation affects CPD removal. (A) Sample images of HaCaT nuclei, stained by DAPI and treated with either TSA or 4x PBS. (B) Quantification of the chromatin compaction state by the intensity histograms of the DAPI stained cell nuclei. TSA treatment (orange) induces an enrichment in the dim DAPI intensity bins compared to controls (blue line), while 4xPBS treatment enriched the DAPI bright (compacted) fractions (green line). (C) Effects of TSA treatment on the CPD removal after exposure to UVB or the combination of UVB and nIR. TSA pretreatment enhanced the removal of CPD removal similar to the nIR co-exposure (orange vs. pale green line). Combination of TSA and nIR did not additionally affect the CPD removal (dark green). (D) Artificial compaction of chromatin by 4xPBS treatment eliminated the faster removal of CPDs seen with nIR co-exposure, but did not significantly slow down the removal of CPDs when combined only with UVB exposure. (E) Effect of UVB, nIR and the combination of UVB and nIR on chromatin compaction. Sample images of confocal mid nuclear sections, represented in a false colour lookup table to highlight the differences. (F) Quantification of changes in the DAPI intensity distribution at time points up to 24 h. DAPI intensities were divided in 7 equal relative classes. Lines represent the means and the shaded areas the extend of the standard error of the mean. The datapoints show the mean values of at least three replicates and the error bars represent the standard error of the mean. Curves are fitted single exponential decay curves.