In vivo co-immunoprecipitation. (A) Extracts were prepared from cells expressing untagged Rrp5p (lane 1) or ProtA-Rrp5p (lane 2), treated with IgG Sepharose beads. Total RNA was isolated from the bead fraction and subjected to Northern analysis using probe 2, located closely downstream from site A2 (cf. Fig. 1). Only the region of the gel containing the 27S precursors is shown. (B) Total RNA was isolated from both the supernatant (lanes 1,3) and bead (lanes 2,4) fractions and subjected to primer extension analysis using probe 5, spanning the 3′ end of 5.8S rRNA (cf. Fig. 1). (Lanes 1,2) Samples prepared from cells expressing untagged Rrp5p; (lanes 3,4) samples prepared from cells expressing ProtA-Rrp5p. The stops corresponding to sites B1L and B1S are shown.
