(A) Protein blots and quantification of biotinylated proteins labeled by FL versus truncated SUGP1-DHX15 interaction-reconstituted split-APEX activity. Ponceau S protein stain, loading control for total protein; streptavidin IRDye, detection of biotinylated proteins; FRB-nls, FRB control protein fused with an SV40 NLS; ΔGp, G-patch domain truncation; Gp-nls, G-patch domain alone fused with an SV40 NLS.
(B) Fluorescent microscopy images of biotinylation signals (streptavidin, magenta), antibodies detecting HA-tagged SUGP1-EX, FL versus Gp-nls (HA, red), FLAG-tagged AP-DHX15 (FLAG, green), nuclear DNA dye (DAPI, blue), and merged channels.
(C) A sampling-and-recruitment model of DHX15-SUGP1 interaction during early-splicing QC.