Inefficient recruitment of DDX39B impedes pre-spliceosome assembly on FOXP3 introns

Recruitment of DDX39B to FOXP3 intron 11 requires its 5′SS and py tract. Western blot analyses of U2AF2 and DDX39B binding to (A) full-length constructs F3i11wt-tobra and F3i11pU-tobra, or (B) hemi-intron constructs F3i11wt3′end-tobra and F3i11pU3′end-tobra, after 0, 15, and 30 min of IVS incubation. Each panel represents triplicate experiments with full-length constructs or duplicate experiments with hemi-intron constructs using different nuclear extract preparations.