FIG. 2.

(A) The putative splicing enhancer present in the GAR fragment (black) was substituted for the ASLV enhancer (white) in the downstream exon of the enhancer-dependent splicing reporter substrate dsx-ΔE. (B) In vitro splicing reaction of the dsx substrates in HeLa cell nuclear extract (NE) (lanes 1 to 3) or splicing-deficient HeLa S100 cytoplasmic extract (lanes 4 to 10). S100 extract was complemented with total the SR protein preparation (lane 5) or with single SR proteins (lanes 6 to 10). All of the single SR proteins activated splicing of a β-globin splicing substrate with equal efficiency (data not shown).