IRF2BP1 and SRRT, identified using Coilin-APEX2, are enriched in CBs. (A) Volcano plot showing the location of TOE1 (known component) and IRF2BP1 (new component) in teal and EFTUD2 (known component) and SRRT (new component) in orange. (B) Immunofluorescent staining of previously known and new CB components using α-coilin (magenta) and antibodies specific to either high enrichment, high significance components (TOE1 and IRF2BP1, top) or low enrichment, low significance components (EFTUD and SRRT, bottom) (cyan). Scale bars = 10 µm. (C) Colocalization analysis of coilin with IRF2BP1, EFTUD2, and SRRT. CBs were identified from the coilin channel and cropped symmetrically around their center of mass. Sub-images at the same position in the other channel were also cropped. Averaged images were generated for each channel, and Pearson’s correlation coefficient (PCC) was calculated from the averaged images (see Materials and methods). Scale bars = 0.5 µm. (D) Immunofluorescent staining of SMN or coilin (magenta) and IRF2BP1 (cyan), showing IRF2BP1 is not in gems. Representative single nucleus with accompanying line profile plots showing intensities through a single CB. (E) Immunofluorescent staining of coilin (magenta), IRF2BP1 (cyan) or snRNPs (cyan) after siRNA knockdown of coilin or IRF2BP1, as indicated. Scale bars = 10 µm.