Fig. 4: Local chromatin compaction is influenced by the cell cycle phase and cell passaging.

a–c FRET-FISH score distributions in different cell cycle phases, for three of the six loci probed by FRET-FISH on chrX in female mouse embryonic fibroblasts (MEFs). Measurements from three replicate experiments pooled together are shown. G1 Hoechst^High and G1 Hoechst^Low indicate cells in G1 phase with values of Hoechst 33342 nuclear fluorescence intensity in the top and bottom quartile of the corresponding intensity distribution, respectively. Boxplots extend from the 25th to the 75th percentile, horizontal bars represent the median, and whiskers extend from –1.5×IQR to +1.5×IQR from the closest quartile, where IQR is the inter-quartile range. Black dots, outliers. In each boxplot, the minimum and maximum are defined, respectively, by the uppermost and lowermost outlier dot or extremity of the corresponding whisker. n, number of FRET signals analyzed. P, Wilcoxon test, two-tailed. d–f FRET-FISH score distributions in G1 and non-G1 cells for the same loci shown in (a), in one of three replicate (Rep) experiments. The inflection point in each bimodal distribution was used to separate between the lower (green) and higher (orange) FRET-FISH score mode corresponding, respectively, to a less and more compact chromatin state. The percentages indicate the proportion of FRET signals in each group. n, number of FRET signals analyzed. g–i Same as in (d–f) but comparing MEFs cultured for less (Low passage) or more (High passage) than 10 passages. Source data for all the plots shown in the figure are provided as a separate Source Data file.