Fig. 4

Super-resolution Stochastic Optical Reconstruction Microscopy (STORM) shows nuclear co-localization of nucleophosmin and phospho-RAD52. a) Representative images of NPM1 immunostaining (green) in the nuclei (white oval traces in top panels) of cells treated with etoposide or vehicle control. Red boxes indicate area of increased magnification in bottom panels; yellow arrows indicate nucleoli; white arrows indicate NPM1 clusters. b-c) Quantification of NPM1 clustering within the nucleoplasm of 3 cells with and without etoposide treatment. ****P < 0.0001, as determined by unpaired student’s t-test, error bars are SEM. d) Representative super-resolution analysis of U2-OS cells treated with etoposide to induce DNA DSBs or vehicle control then stained with antibodies against NPM1 and pRAD52. Colored heat-map where red indicates positive spatial overlap of NPM1 and pRAD52 (correlation coefficient r = 1) and blue indicates negative correlation (r = − 1). E) Numerical quantification of NPM1 and pRAD52 co-localization in the nucleus, n = 10 cells for each condition. Significance was assessed by unpaired student’s t-test (**P < 0.01); error bars are SEM