Skip to main content
. 2010 Apr 6;1(3):284–297. doi: 10.4161/nucl.1.3.11969

Figure 6.

Figure 6

Changes of chromatin proximity patterns during mitosis are not affected by the spindle topography. (A and B) Centrosomes in living RPE-1 cells were visualized by GFP-FOP. The spindle axis was defined by a line through the centrosomes. Activation of paGFP-H4 fluorescence was performed at prophase either parallel (A) or perpendicular (B) to the spindle axis. Although the fidelity of transmission of global chromosome positions appeared higher in (A) than in (B), additional experiments (C–F) provide evidence against this impression. (C–E, upper row) In roughly half of a prophase nucleus photobleaching of mRFP-H2B (red) was performed along its short axis (C), whereas photoactivation of paGFP-H4 (green) was induced along its long axis (D). (C–E, lower row) The resulting daughter nuclei show coherent regions with mRFP fluorescence, but scattered patches of paGFP fluorescence. Of particular interest are the zones of overlap between red and green fluorescence in the daughter nuclei (E). These zones demonstrate patches of green fluorescence within contiguous areas of red fluorescence. This result provides direct evidence that chromatin proximity patterns changed strongly independently of whether fluorescent labeling was performed parallel or perpendicular to the spindle axis. (F) Photoactivation of paGFP-H4 fluorescence in a quarter of a prophase nucleus resulted in daughter nuclei with patches of green fluorescent chromatin scattered over one nuclear half. (G–I) Schemes explaining the outcome of experiments with induction of paGFP-H4 fluorescence in half of prophase nuclei, either parallel to the spindle axis (G) or perpendicular to it (H), as well as in a quarter of a prophase nucleus (I). Top: Arrows point at the centrosomes and define the spindle axis. Filled symbols represent chromosomes after activation of paGFP-H4 fluorescence, open symbols chromosomes with mRFP-H2B fluorescence only. Bottom: Schemes of the metaphase plate with daughter nuclei. In (H and I) the upper pair of daughter nuclei represents mirror like symmetry, the lower pair translational symmetry (for further explanation see text).