Fig. 1. Comparison of the localization of endogenous SF3a subunits with other splicing components. (A-E) HeLa cells were permeabilized with Triton X-100, fixed with paraformaldehyde and treated with antibodies against the following proteins: (A) SF3a60 and SF3a66; (B) SF3a66 and SF3a120; (C) SF3a60 and SC35; (D) p80-coilin and SF3a66; (E) SF3a60 and U2 B''. (F) Cells were hybridized with a 2' O-methyl oligoribonucleotide complementary to U2 snRNA and immunostained with an anti-SF3a66 antibody. Images shown in all left panels were obtained after staining with FITC-coupled secondary antibodies. Images shown in middle panels were stained with rhodamine-coupled secondary antibodies. The right panels show computer-generated overlays of the two images. CBs appear in green in panel (D), and red in panels (E) and (F). Arrows in (E) and (F) indicate the absence (left panels) or presence (middle and right panels) of CBs. Bar, 10 µm.