RNA is important for coilin oligomerization and CB formation. (A) Microinjection of RNase A into HeLa^coilin-EGFP stable cell line followed by time-lapse. The images represent from left to right: preinjection, 70 s after injection, and 140 s after injection. Scale bar represents 5 µm. (B) RNAase injection disrupts fibrillarin but not SMN localization. RNase A was microinjected together with 70-kD dextran-TRITC into the nucleus of HeLa^coilin-EGFP cells and fibrillarin. and SMN proteins were detected by indirect immunofluorescence. Scale bar represents 5 µm. Number of CBs and gems in four microinjected cells was quantified, and the graph shows individual measurements, mean, and standard error of the mean. (C) Immunoprecipitation of coilin-EGFP with anti-GFP antibody with or without RNase A treatment. Quantification of three independent experiments is shown with mean and standard error of the mean. The signals after immunoprecipitation were normalized to relevant inputs, which were set to 1. (D) Coilin forms complexes with RNA. HeLa^coilinKO cells transfected with EGFP-coilin^WT were illuminated with UV light to cross-link proteins and RNA. Cell extract was treated with or without RNase I, and EGFP-coilin-RNA adducts immunoprecipitated by anti-GFP antibodies and detected by western blotting. Source data are available for this figure: SourceData F4.