Figure 8.

Photobleaching experiments on mitotic chromosomes. (A) FRAP (as described in Fig. 5) of metaphase chromosomes in cells expressing GFP chimera of topo IIα (with and without 100 μM VM 26), topo IIβ (VM 26-treated) or histone H3 after bleaching a circular area of 3 μm diam. Bleaching of topo IIβ–GFP-labeled chromosomes not treated with VM 26 was not possible, as they were obscured by large amounts of cytosolic topo IIβ–GFP (Figs. 3 and 4 B). (B) FLIP (as described in Fig. 7) of a chromosomal and a cytoplasmic region (black and white circles) after bleaching of another chromosomal area (white circle) in a metaphase cell expressing topo IIα–GFP.