Figure 1.

Prp5 is not required for splicing after prespliceosome formation. (A) A schematic diagram showing early steps of spliceosome assembly and the involvement of Prp5 and Sad1. (B) Splicing reactions were carried out in Sad1-depleted extracts (lanes 1,2,5–12), and the reaction mixtures were then mock-treated (lanes 5–8) or depleted of Prp5 (lanes 9–12). Purified Sad1 and/or recombinant Prp5 proteins were added as indicated to the reaction mixtures, which were then further incubated for 20 min. The splicing reaction was carried out in Prp5-depleted extracts without (lane 3) or with (lane 4) the addition of Prp5.