(A) Western blot analysis of splicing extracts prepared from strains overproducing Snt309p alone (lanes 1), both Snt309p and Prp19p (lane 5), or Prp19p alone (lane 6). Lane 2 is the cell pellet from the preparation of the splicing extract of lane 1. Lane 3 represents the total cell lysates from the strain overproducing Snt309p alone. Equivalent amounts of cell extracts were loaded on each lane. Ex, splicing extract; P, cell pellet; T, total lysates; M, molecular mass marker. (B) Complementation of the ΔSNT309 extract (Ext) by Prp19p–Snt309p binary complex. (Lane 1) Wild-type (WT) extract; (lanes 2–6) ΔSNT309 extracts. Fractions used for complementation (Comp): the Prp19p-associated complex (Cp; lane 3); affinity-purified fractions (AF Fr) overproducing Prp19p and Snt309p (lane 4), overproducing Prp19p only (lane 5), and overproducing no protein (lane 6). (C) Reconstitution of the Prp19p-associated complex. ΔSNT309 extracts (lanes 2–6) were added to an anti-HA antibody column-purified fraction from extracts overproducing both Snt309p and Prp19p (lanes 3 and 6), Prp19p only (lane 4), or normal extracts (lane 5), and then precipitated with the anti-Ntc20p antibody (lanes 1–5) or nonspecific (N) antibody (lane 6). Lane 1, wild-type extract.