Expression of mutant Y805F, but not AEEA, GFP:Top2 correlates with chromatin bridge breakage in cytokinesis. (A–C) Localization of GFP or ATM at the bridge DNA next to the midbody in BE cells expressing siRNA-resistant (R) WT, Y805F, or AEEA GFP:Top2R proteins, or GFP-only, in the absence or presence of Top2α siRNA. (D–F) Localization of INCENP at the midbody ring. (G–I) Mean intensity of GFP, ATM, or INCENP at the bridge DNA next to the midbody or at the midbody ring. Mean ± SD from n cells. Values in WT (G) or GFP (H and I) were set to 1. (J) Percentage of broken DNA bridges in BE cells transfected as in H and I. Mean ± SD from three independent experiments (n > 120). ***, P < 0.001 (ANOVA and Student’s t test). Broken chromatin bridges are indicated by dotted arrows. Arrowheads indicate DNA knots. Midbodies (boxed areas) were reexported and are shown at higher magnification. Numbers below/next to each bar indicate n. Scale bars, 5 μm.
