Fig. 4. Localisation of c-Myc in relation to fibrillarin. (A) c-Myc-GFP is predominantly located in the nucleoplasm of cells in the absence of proteasome inhibitors. Confocal images showing the distribution of c-Myc-GFP and fibrillarin in untreated COS-7 cells are shown in a and b, respectively. The distinct localisation of c-Myc-GFP and fibrillarin is shown in c-e. In c, the confocal images in a and b are overlaid. The relative fluorescence intensity (RFI) from c-Myc-GFP (green) and fibrillarin (red), along the white line in c is quantified in d. (e) Reconstitution of the stack of confocal xy plane images; e' and e'' show yz and xz sections through the stack of images, respectively. The positions of the sections are shown by the fine white lines in e. Bar, 10 µm. (B) Nucleolus-associated c-Myc-GFP accumulates in regions adjacent to but distinct from the fibrillarin marker for the dense fibrillar region of the nucleolus in proteasome-inhibitor-treated cells. Confocal images showing the distribution of c-Myc-GFP and fibrillarin in cells treated with proteasome inhibitor are shown in a and b, respectively. The distinct localisation of c-Myc-GFP and fibrillarin within the nucleolus is shown in c-e. In c the confocal images in a and b are overlayed. The relative fluorescence intensity (RFI) from c-Myc-GFP (green) and fibrillarin (red), along the white line in c is quantified (d). (e) Reconstitution of the stack of confocal xy plane images; e' and e'' show yz and xz sections through the stack of images, respectively. The positions of the sections are shown by the fine white lines in e. Bar, 10 µm.