Fig. 6

Comparative topology of SC35 and RNA Pol II Ser2P, markers for transcriptional activity in relation to chromatin density maps. a 3D-SIM light optical mid-sections from whole 3D acquisitions of nuclei and representative inset magnifications delineating DAPI stained DNA (gray), immuno-stained SC35 (green) and RNA Pol II Ser2P (red). SC35, an integral part of splicing speckles, is seen almost exclusively in the IC compartment, while RNA Pol II Ser2P shows a preferential localization at decondensed chromatin sites or at the surface of compacted chromatin domain clusters (compare Fig. 5). Scale bars 2 µm; insets 0.5 µm b graphs highlighted with yellow background: relative signal distribution of SC35 (green) and RNA Pol II Ser2P (red) within respective DAPI defined DNA intensity classes. Graphs highlighted with light-blue background quantified levels of relative enrichment (positive values) or depletion (negative values) of SC35 (green) and RNA Pol II Ser2P (red) signals relative to the DAPI signals confirm the massive enrichment of SC35 signals in class 1 reflecting the IC compartment. n Number of analyzed nuclei; error bars standard deviation; p < 0.001 for DAPI vs. SC35 and RNA Pol II Ser2P, and for SC35 vs. RNA Pol II Ser 2P