Fig. 3. Topo II depletion causes abnormalities in chromosome structure, but does not affect histone H3 phosphorylation on serine¹⁰. All images are from cultures at 72 hours after addition of Topo II dsRNA. (A-A'") Control RNAi-treated metaphase cell. (B-B'") Prometaphase cell with abnormal chromosome morphology viewed parallel to spindle axis. (C-C'") Two metaphase cells, one of which has a highly elongated chromosome arm extending to one spindle pole. Both are viewed nearly perpendicular to the spindle axis. (A-C) DAPI staining for DNA; (A'-C') anti-tubulin shows the mitotic spindle; (A",B") histone H3 phosphorylated on serine¹⁰ is stained with a specific antibody; (A'"-C'") merged images (DAPI is blue, tubulin is red, histone H3 is green. Scale bar: 5 µm.