FIGURE 1.

Utp10 and Utp20 are associated with early pre-rRNAs and snoRNAs. (A) The 35S pre-rRNA contains the sequences of the mature 18S, 5.8S, and 25S rRNAs, which are separated by internal transcribed spacers 1 and 2 (ITS1 and ITS2) and flanked by the 5′ and 3′ external transcribed spacers (5′ETS and 3′ETS). Locations of the different oligonucleotides used in this study are shown. (B, C) Northern analysis of rRNAs coprecipitated with Protein A–tagged versions of Utp10 and Utp20 (lanes 3–6, 9–12) or from extracts of cells lacking a tagged protein (lanes 1,2,7,8). Immunoprecipitation was performed on cell extracts using IgG-Sepharose. RNAs were extracted from the pellet after precipitation (lanes IP) or from total cell extract (lanes T) corresponding to 5% of the input for the immunoprecipitation reactions in panel B (1.2% denaturing agarose gel) or 10% of the input in the panel C (8% polyacrylamide/urea gel). Following separation, RNAs were transferred to a nylon membrane and hybridized with the anti-sense oligonucleotides indicated to the right of each panel.