Fig. 3. Microstructures are mobile within stressed nuclei. (A) The movement of a PML-containing microstructure was characterized in a nucleus of a HEp-2 cell stably expressing GFP-PML I after 1 hour recovery period following heat shock at 43°C for 30 minutes (a movie showing the movement of this microstructure, which is contrast enhanced in A can be seen in Movie 2, http://jcs.biologists.org/supplemental/). (B) Its position was plotted at each time interval (18 seconds, every third frame of the movie), indicated by white diamonds. (C) The cumulated distance of its travel is plotted as a function of time. The total time recorded was 24x18=432 seconds. Three putative domains or regions (I-III) are indicated in both (B) and (C). (D) Mean squared displacement was calculated (Chubb et al., 2002) for slow moving (circles, n=37) and fast moving microstructures (squares, n=10) and plotted against t. The initial slope of the curve was used to determine diffusion constants. Both curves plateau indicating that the diffusion of both sets of microstructures is constrained. 1 pixel² corresponds to 0.03 µm².

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