Fig. 5

PKMYT1-induced NPM1 S260 phosphorylation promotes efficient DSB repair. a Western blot analysis of the expression of PKMYT1, phosphorylated-NPM1 S260, and phosphorylated-NPM1 T199 in OS cells after being treated with various concentrations of DDP. b–d Western blot analysis of the effect of DDP and IR on NPM1 S260 phosphorylation after PKMYT1 knockdown or inhibition with RP6306. e Western blot analysis of the impact of DDP and IR on NPM1 S260 phosphorylation following the overexpression of NPM1 S260 dephosphorylation mutant plasmid. f After transfection as indicated siRNAs for 48 h, HEK293T cells were collected and subjected to co-immunoprecipitation experiments followed by western blot analysis. g HEK293T cells were transfected with indicated siRNAs for 48 h and treated with or without cisplatin (1 μM) for 24 h before harvesting the cells for co-immunoprecipitation and Western blot. h HEK293T cells were treated with or without RP6306 (2 μM) for 24 h before harvesting the cells for co-immunoprecipitation and Western blot. i HEK293T cells were treated with or without RP6306 (2 μM) and cisplatin (1 μM) for 24 h before harvesting the cells for co-immunoprecipitation and Western blot. j HEK293T cells were transfected with indicated plasmids for 24 h and treated with or without cisplatin (1 μM) before harvesting the cells for co-immunoprecipitation and Western blot. k–l Immunofluorescence analysis of the effect of NPM1 S260 phosphorylation on IR-induced BRCA1 foci. NPM1 knockout U2OS cells were rescued with either wild-type NPM1, NPM1 S260A mutant and NPM1 S260D mutant, with or without IR (10 Gy) treatment. Representative images are shown in k, and the number of BRCA1 foci per group was calculated in l. Approximately 100 cells were counted per group. Data are expressed as the mean ± SEM from three biological replicates. Statistical analysis was performed using Student’s t test, p value as indicated. Scale bar, 10 μm. m–n Immunofluorescence analysis of PKMYT1 wild-type and PKMYT1 knockout U2OS cells with or without IR (10 Gy) treatment. Representative immunofluorescence images were shown in m, and the number of BRCA1 foci per group was calculated in n, p value as indicated. Scale bar, 10 μm. o–p NPM1 knockout U2OS cells were rescued with indicated plasmids for 24 h, and immunofluorescence analysis of cells exposed to 10 Gy IR and recovered for 1 h. Representative immunofluorescence images were shown in o, and the number of RAD51 foci per group was shown in p, p value as indicated. Scale bar, 10 μm. q–r Immunofluorescence analysis of PKMYT1 wild-type and PKMYT1 knockout U2OS cells with or without IR (10 Gy) treatment. Representative immunofluorescence images were shown in (q), and the number of RAD51 foci per group was calculated in r. Scale bar, 10 μm. s, t Immunofluorescence analysis of PKMYT1 wild-type and PKMYT1 knockout cells with or without IR (10 Gy) treatment. Representative immunofluorescence images were shown in (s), and the number of RAP80 foci per group was calculated in t, p value as indicated. Scale bar, 10 μm. u HR assay in PKMYT1 wild-type and PKMYT1 knockout HEK293T cells, with BRCA1 knockout as control. Data are presented as the mean ± SEM from three replicates. Each group included over 1000 cell counts. P value as indicated. v NHEJ assay in PKMYT1 wild-type and PKMYT1 knockout HEK293T cells, with 53BP1 knockout as control. Data are presented as the mean ± SEM from three replicates. Each group included over 1000 cell counts, p value as indicated