Fig. 3

Change in global chromatin architecture of radio-resistant cells. a Cell cycle profile of P and RR synchronized in G₀/G₁ phase. b Chromatin architecture alterations analyzed by micrococcal nuclease (MNase) assay resolved on 1.8% TAE-agarose gel to visualize the digestion pattern. Time points indicate the duration of incubation of nuclei with MNase. c Densitometry based representation of MNase digestion. Black arrows point to areas of overall change in chromatin architecture between P and RR. Red horizontal line and red arrows point towards conversion of high molecular weight genomic DNA to polynucleosomes at 5-min time point. d Western blots depict levels of histone H1 and HP1α in P and RR. PVDF membrane showing core histones serves as loading control. e Representative z-stack projection images of HP1α immunofluorescence in P and RR. DAPI staining depicts nuclei. Scale bar - 10 μm (f) Graph represents the average nuclear intensity of HP1α quantified from n = 50 nuclei from different fields. Scale bar- 10 μm. Parental MCF7 is denoted as “P” and radioresistant cell line is denoted as “RR.” Statistical analysis is done by Student’s t test. L is 100 bp ladder. ^*p < 0.05, ^**p < 0.01, a.u.—arbitrary units and mins.—minutes. Images were processed using LSM browser software and Image J for confocal microscopy and MNase densitometry, respectively