Fig. 4: The increase in H3K4me2 levels is actively induced by live bacteria. | Nature Communications

Fig. 4: The increase in H3K4me2 levels is actively induced by live bacteria.

From: Epithelial cells maintain memory of prior infection with Streptococcus pneumoniae through di-methylation of histone H3

Fig. 4

A Representative images of immunofluorescence detection of nuclear H3K4me2 in A549 UI or infected with Spn live and Spn inactived (1° and PI, MOI 20) at time γ. Cells stained for H3K4me2 (GFP; green) and DAPI (blue). Microscopy images were taken at ×20 magnification, and the scale bar represents 100μm. B Quantification of H3K4me2 normalized to the segmented nuclei using DAPI signal. Data points expressed as fold change of mean fluorescence intensity of infected cells 1° and PI to UI (MOI 20) with sp live and sp inactived at time g. Graphs display quantification from n = 3 to 7 biological replicates with the mean values ±SD for each condition. Statistical significance was determined by one-way ANOVA with Fisher’s LSD test (ns = not significant, **p = 0.0012, ***p = 0.0001, ****p < 0.0001). C Quantification of H3K4me2 intensity normalized to the segmented nuclei using DAPI signal at time β and γ 1° (MOI 10) and UI. Box and whiskers plot with line denoting the median value from n = 754 to 1075 nucleus by conditions in the same experiment. Statistical significance was determined by one-way ANOVA comparing means with Tukey’s multiple comparison test (****p < 0.0001). D Quantification of H3K4me2 according to Multiplicities of infection (MOI) normalized to the segmented nuclei using DAPI signal at time γ. Histogram shows the mean fluorescence intensity ±SEM from n = 435 to 480 nuclei by conditions in the same experiment. Statistical significance was determined by one-way ANOVA with Fisher’s LSD test (****p < 0.0001). E, F Quantification of H3K4me2 intensity after infection with E Spn mutant without capsule (−) or F Spn mutant without pilus (−), compared to wildtype Spn (+). H3K4me2 intensity is normalized to the segmented nuclei using DAPI signal at time γ post 1° (MOI 20) and UI. Graphs display quantification n = 300 nuclei/condition/exp. Box and whiskers plot with line denoting the median value. Statistical significance was determined by one-way ANOVA comparing means with Tukey’s multiple comparison test (****p < 0.0001). Source data are provided as a Source Data file for A–F.

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