Fig. 2. Coilin mutants display unregulated nuclear body formation. Upper panels, HeLa cells were transfected with GFP fused to the N-terminus of coilin (left), GFP fused to the C-terminus of coilin (middle) or a GFP-tagged truncation of coilin (1-481, right). The GFP-coilin(1-481) foci colocalized with other CB markers (SMN and fibrillarin) when transfected into HeLa cells (data not shown). Note that several out-of-focus dots appear blurred. In the lower panels, deletion of the nuclear localization signals (residues 106-234) in the GFP-coilin background results in exclusively cytoplasmic localization without foci in HeLa cells (left). Deletion of the NLSs in the coilin-GFP background results in a similar pattern, with the exception that nuclear foci are detected. Although the bulk of the fluorescence was cytoplasmic, two populations of cells were observed, some with faint nuclear foci and others with brighter foci (middle). When transfected into coilin knockout MEFs, this same coilinNLS-GFP construct localized solely to the cytoplasm (right).