Topo IIα and IIβ are dissociated from the chromatin during apoptosis. Logarithmically growing (A, C, and D) and apoptotic HL-60 cells treated with Ara-C for 5 hours (B and E) are immunostained with topo IIα-specific 8D2 (A and B) and topo IIβ-specific 3G3 monoclonal antibodies (C through E). Topo IIα and IIβ signals are green arising from the FITC-conjugated secondary antibody, and PI counterstaining for DNA is red.