Proteasome inhibition correlates with impaired localization of Mre11 and ATM to the bridge DNA next to the midbody. (A–E) Localization and mean intensity of ubiquitin at DNA knots in intact chromatin bridges. BE cells were extracted with the differential retention assay protocol without treatment (control), after transfection with Top2α siRNA, or after treatment with 10 μM MG132 or 10 μM MLN7243 for 4 h. (F–O) Localization and mean intensity of Mre11 or ATM at the bridge DNA next to the midbody. Mean ± SD from n cells. Values in control were set to 1. ***, 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.