FIG. 4.

The ∼50S splicing complex contains all five major spliceosomal snRNAs. A) Biotinylated NRS-Ad3′ RNAs were incubated in splicing reactions and layered onto a sucrose gradient in the absence of heparin. The ∼50S peak fractions were affinity selected using streptavidin-agarose beads. The affinity-selected RNA was harvested and electrophoresed, and a Northern analysis was performed, using probes for the major spliceosomal snRNAs. The HeLa control lane contains total RNA extracted from HeLa nuclear extract. B) Affinity selection was carried out as described for panel A. The Northern blot was probed to detect the five major spliceosomal snRNAs and then reprobed with a probe complementary to U11 snRNA. The lane marked “Beads” exhibits a control affinity selection carried out in the absence of biotinylated RNA.