Fig. 5. Efficient formation of a U2-dependent complex by splicing factors associated with the RNA Pol II-containing complex.
Nuclear extracts (lanes 2–5) and the RNA Pol II-containing complex (Holo; lanes 10–13) were incubated with an adenovirus pre-mRNA containing a splicing cassette. A nuclear extract (NEΔU2; lanes 6–9) and the RNA Pol II-containing complex (HoloΔU2; lanes 14–17) depleted of snRNA U2 were used as controls. Splicing complex formation was monitored over time as indicated. The positions of the H and A complexes formed in nuclear extracts are indicated. The RNA Pol II-containing complex also leads to the assembly of a U2-dependent complex (RP) that nearly migrates with the A complex.