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. 2014 Jul 1;107(1):55–65. doi: 10.1016/j.bpj.2014.05.027

Figure 2.

Figure 2

Changes in G1 interphase chromatin compaction during DNA damage response. (A) G1 interphase HeLa cell expressing EGFP with the chromatin marked by Hoechst 33342, scale bar equals 3 μm. The line scan selected for pair correlation analysis of EGFP molecular flow with respect to damaged and undamaged chromatin superimposed at position 1 and 2, respectively. DNA damage is induced along the line scan at position 1 by microirradiation and then the chromatin is measured as position 1 and 2 at 0–10 min post-damage. (B and C) Intensity profile of free EGFP (green) and DNA (blue) along the line scan at position 1 and 2, respectively, before DNA damage. The highest density chromatin region along each line (pixels 8–16 in panel B and pixels 36–60 in panel C) excludes EGFP. Pair correlation analysis along each line scan reveals the high-density chromatin regions to cause disconnect in molecular flow (indicated by vertical red arrows). (D) The average time delay for EGFP molecular flow inside, outside, and in-between interphase chromatin before DNA damage (representative data shown in panel B) and how these times are changed after DNA damage (representative data shown in panel E). (E) Intensity profile of free EGFP and DNA along the line scan at position 1 at 0 min after DNA damage reveals the highest-density chromatin region (pixels 8–16) to no longer exclude EGFP. Pair correlation analysis along this line at pCF(5) reveals the chromatin density region to now be accessible on a timescale of 0.5 ms (indicated by horizontal red arrows). (F) Intensity profile of free EGFP and DNA along the line scan at position 2 at 0 min after DNA damage shows the high-density chromatin region between pixels 36 and 60 to exclude more EGFP. Pair correlation analysis along this line scan at pCF(5) reveals this chromatin density region be less accessible (indicated by vertical red arrows). (G) Intensity profile of free EGFP and DNA along the line scan at position 1 at 10 min after DNA damage, shows the high-density chromatin region between pixels 8 and 16 to remain accessible to EGFP. Pair correlation analysis along this line scan at this time reveals the chromatin density region to be slightly less accessible on a timescale of 5 ms (as indicated by horizontal red arrows). (H) Intensity profile of free EGFP and DNA along the line scan at position 2 at 10 min after DNA damage shows the high-density chromatin region to remain inaccessible to EGFP (as indicated by horizontal red arrows). To see this figure in color, go online.