Identification of TOE1 function in regulating Cajal body homeostasis. (A) Schematic workflow showing how the function of proteins localized to Cajal bodies was studied (please also see Fig. S3, C and D). (B) TOE1 is an integral component of Cajal bodies. The localization of TOE1 in HeLa cells was determined by coimmunostaining using anti-TOE1 and anti-coilin (top) or anti-SMN (bottom). Bars, 10 µm. (C) Proteomic analysis of TOE1-containing protein complexes. A cartoon (top part) or a list (bottom part) was presented. (D) SFB-tagged NUAK2 (negative control), TOE1, and TCAB1 were ectopically expressed in HEK293T cells. Pull-down experiments were conducted using streptavidin beads, and immunoblotting was performed with anti-Flag and the indicated antibodies. The asterisk indicates a nonspecific band. (E) Association of endogenous TOE1 and coilin was confirmed by co-IP experiments. Immunoprecipitation (IP) was conducted using the anti-coilin antibody or normal rabbit IgG. WB, Western blot.