SC35 reconstitution of splicing in U2AF-depleted reactions is substrate-specific. Splicing of PIPβG pre-mRNA in mock (lane 1), U2AF-depleted (lane 2), U2AF65-reconstituted (lane 3), and SC35-reconstituted (lane 4) extracts. Splicing of PIP85.A in mock (lane 5), U2AF-depleted (lane 6), U2AF65 reconstituted (lane 7) and SC35 reconstituted (lane 8) extracts.