Enrichment of CB proteins using proximity biotinylation identifies seventy new CB proteins. (A) Immunofluorescent staining of coilin-AEPX2 labeled by α-V5 antibody (magenta) and α-SMN antibody (cyan). (B) Immunofluorescent staining of APEX2-NLS and ΔNTD-APEX2 labeled by α-V5 antibody (magenta) and α-coilin (cyan). (C) Streptavidin Blot of fractionated coilin-APEX2 cells ± BP and H₂O₂ showing endogenously biotinylated proteins (*) and biotinylated proteins after treatment (top). Primary antibodies showing localization of proteins in fractions; α-V5 antibody is a marker for coilin-APEX2, α-GAPDH antibody is a marker for cytoplasm, α-H3 antibody is a marker for nucleus. (D) Streptavidin Blot of biotinylated proteins pulled down from nuclear lysates ± BP and H₂O₂ treatment. (E) Venn diagram of statistically enriched CB proteins relative to ΔNTD-APEX2 (teal) and APEX2-NLS (orange) compared to known CB proteome (yellow). (F) CB proteins that are enriched in the 100 hits. The percent of proteins in the human and nuclear proteome and of the enriched hits that localize to CBs. (G) Venn diagram of statistically enriched CB proteins against both controls (teal) compared to coilin-BioID (orange) (Go et al., 2021) and known CB proteome (yellow). (H and I) GO-term analysis of proteins enriched in coilin-APEX2. The 10 most significant hits along with the −log₁₀ of their P values are displayed, CB-associated GO terms are highlighted in yellow. Source data are available for this figure: SourceData FS1.