FIG. 2.

Rds3p is present in the yeast spliceosome. (A) Western blot of whole-cell yeast extracts (lanes 1 to 3) and affinity-purified splicing complexes (lanes 4 to 7) probed with a TAP-specific antibody. Spliceosomes were assembled for 45 min on biotin-substituted (+) or unmodified (−) RPS17A pre-mRNA in wild-type extracts (Rds3p) and in extracts where the epitope-tagged Rds3-TAP or Clf1-TAP served as the only source of these essential proteins. The positions of the relevant tagged proteins are indicated on the right. Strept, streptavidin.