FIG. 2.

Prp43p is associated with several spliceosomal snRNAs and pre-rRNAs and with mature 18S and 25S rRNAs. Immunoprecipitation experiments were carried out using IgG-Sepharose and total cellular extracts from the parental strain lacking a tagged protein (No TAP-TAG; lanes 1 and 2), or from strains expressing Prp43p-TAP (lanes 3 and 4) or Prp22p-TAP (lanes 5 and 6). RNAs were extracted from the pellets obtained following precipitation (Ip) or from an amount of input extract corresponding to 1/150 of that used for the precipitation (Tot) and analyzed by the Northern blot technique or the primer-extension procedure (to detect 35S, 27SA2, and 27SB pre-rRNAs). cDNA products obtained by primer extensions were separated on a 6% sequencing gel, and RNAs were separated and detected as described in the legend of Fig. 1B. Signal intensities were measured by phosphorimager scanning to derive the percentage of input RNAs precipitated (indicated below each Ip lane). bg, background value.