Fig. 4: 53BP1 maintains the repressive state of heterochromatin.

ChIP-qPCR of 53BP1 at alpha satellite repeats of mcBox (a) and SATIII (b) regions in HEK293T parental, 53BP1 KD and KD reconstituted with GFP-53BP1-FL/WT cells from n = 3 biological replicates. c Transcript levels of Maj and Min SATs measured by qPCR in parental and 53bp1 KO MEFs from n = 6 biological replicates collected from two independent experiments. d Transcript levels of alpha satellite repeats of heterochromatin from parental and stable 53BP1 KD U-2 OS or HepG2 cells from n = 3 biological replicates. Inset: representative protein expression in U-2 OS cells from two independent experiments. Transcript levels of the alpha satellite repeat SATα (e) and mcBOX (f) from HEK293T parental, 53BP1 KD and KD cells reconstituted with GFP-53BP1-FL/WT from n = 3 biological replicates. g Representative single z-plane confocal images of parental, 53bp1 KO and KO MEFs reconstituted with GFL-53BP1-FL/WT. Squares: enlarged areas. Scale bar is 10 μm. h Violin plot of the number of heterochromatin centers visualized by DAPI from indicated number of cells from at least three independent experiments. Data represent mean, 25th, and 75th percentiles with the whiskers extending to the minimum and maximum values. Data represent mean values and SD in (a–f). Statistical analyses in (d) were compared with parental cells. Unpaired two-tailed t test was done by Prism 9.0 with 95% confidence intervals in (a–f) and (h).