Supplemental Material

This article contains the following supporting material:

• Supplemental Figure 1 - Intranuclear location of the mobile trajectory from Fig. 4 The trajectory from a mobile U1 snRNP (marked by an arrow) was taken from a movie acquired at 100 Hz with an integration time of 5 ms per frame. The figure shows the positions of the speckles (green) within the nucleus (grey level image), of the cytoplasm (grey background) and of all trajectories identified in the corresponding movie sequence. Trajectories were color-coded: within the nucleoplasm, blue; within the speckles, yellow; crossing from nucleoplasm to speckles, orange. The field size was 12.8x12.8 μm².

• Supplemental Movie 1 - High-speed movie of single U1 snRNPs within a living cell nucleus The movie was recorded at 200 Hz, and displayed at 15 Hz. Left hand side: original data. Center: overlay of the contrast enhanced and filtered (Gaussian kernel, 1 pixel radius) with the green fluorescence image of the ASF/SF2-GFP fluorescence. Bright green spots marked the positions of splicing factor compartments (speckles). Please note that the ASF/SF2-GFP was not imaged by confocal microscopy. Right hand side: movie data was filtered using a spot-enhancing filter (3 pixel diameter, (Sage et al., 2005)) to improve U1 snRNP visibility with the ASF/SF2-GFP image.

• Supplemental Movie 2 - Mobile U1 snRNP The image sequence shows a mobile U1 snRNP (see Fig. 4). This U1 snRNP was detected in 10 subsequent frames in a sequence acquired at 100 Hz with an integration time of 5 ms per frame. Left hand side: data was contrast enhanced and filtered (Gaussian kernel, 1 pixel radius); right hand side: movie data was filtered using a spot-enhancing filter (3 pixel diameter, (Sage et al., 2005)) to improve U1 snRNP visibility. The overlay of the trajectory with the ASF-GFP image is shown in Fig. 1 in the online supplemental material).