Figure 6

Reduced nuclear mobility of Topo IIβ by ICRF-187. (A) Representative images of FRAP analysis of EGFP-Topo IIβ. HeLa cells transiently expressing EGFP-Topo IIβ or EGFP-Topo IIβ carrying a G180I substitution were pretreated with either 20 µM ICRF-187 or DMSO. A small nuclear area indicated by a white circle in the nucleus was photobleached, and fluorescent images were obtained at the indicated time points. (B) Quantification of fluorescent signals of EGFP-Topo IIβ in FRAP analysis. Fluorescent images were obtained at 5 sec intervals. Mean values with SD from seven individual experiments were plotted. (C) Tight association of endogenous Topo IIβ with nuclear matrices in the presence of ICRF-187. HeLa cells pretreated with ICRF-187 were microirradiated with a pulsed UVA laser. The cells were incubated with detergent-containing (+CSK) or detergent-free (−CSK) buffer and subsequently subjected to fixation followed by coimmunofluorescence of Topo IIβ and Ku70.