Fig. 4: Notch1 activation suppresses the lethality caused by BRCA1 deficiency via cell-cycle regulation.

a Overexpression of ICN1 suppressed the cell death caused by BRCA1 acute knockdown in MCF10A naïve cells. b Quantification analysis by MTT assays regarding the rescue effect of ICN1 on BRCA1 deficiency. Analysis on the 3rd day after Dox and/or lentivirus with shRNA-BRCA1 induction; n = 3 biologically independent experiments. c IF staining and foci counting d and intensity quantification e of γ-H2AX to indicate DNA damage at 48 h after BRCA1 acute knockdown with or without ICN1 overexpression; n = 17–30 independent cell measurements. f Mitotic index analysis of MCF10A cells at 1 h after 0.5 Gy gamma-irradiation treatment. A total of 20,000 cells were counted, and three repeats were used to determine the SD. g Quantification analysis of the relative M-phase portion in the different treatment groups in e; values were normalised to the no-irradiation treatment value for the individual groups; n = 3 biologically independent experiments. The p-value was determined by the t-test with one-tailed distribution. h Dynamic changes in the mitotic index at different time points after 0.5 Gy gamma-irradiation treatment; n = 3 biologically independent experiments. * indicates p < 0.05. i Pulse-chase assay to measure S-G2 and S-M progression. The yellow arrowhead indicates representative cells that progressed to G2 phase at a particular time point. j Fraction of EdU-positive cells entering G2 phase (BrdU-negative) during the chase (n = 1800). k S-M progression indicated by EdU and p-H3 double-positive cells (n = 1100). Data are presented as mean values ± s.d.