Fig. 2. (i) Three dimensional projections of parental HeLa cells fused to cells from line YFPSmBE1 fixed 1,2,3,5,7,9 and 16 hours after heterokaryon formation (A-G). YFPSmB is shown in grayscale in the top panels, the color panels show YFPSmB (green) overlain with Y12 (anti-Sm) staining (red) and anti-p80-colin staining (blue). YFPSmB is seen in the Cajal body by 1hour after fusion (arrows). Accumulation of YFPSmB in speckles is first seen 3 hours after fusion (arrowheads) and increases with time until, by 16 hours after fusion, cells from line YFPSmBE1 are indistinguishable from cells from the parental HeLa line (G). At the 16 hour timepoint, Cajal bodies are still clearly seen in all cells. Parental HeLa cells fused to HeLa cells expressing GFP-ASF/SF2 (H) show accumulation of GFP-ASF/SF2 in speckles (arrowheads) 2 hours after fusion, with no prior accumulation in Cajal bodies seen. Immunodetection of p80-coilin in these cells (color panel, blue channel) demonstrates that Cajal bodies are present in these cells (arrows). Bar, 10 µm. (ii) Quantification of the proportion of YFPSmB in different nuclear compartments over time. The proportion of YFPSmB signal detected in the Cajal body (red) and speckle (blue) compartments are expressed as a percentage of total nuclear fluorescence for early time points after fusion (1-2 hours), timepoints where speckles are beginning to be visible (4-5 hours), and in unfused cells from line EYFPSmBE1.