FIG. 1.

Rrp36p is a nucleolar protein cosedimenting with preribosomes in yeast cells. (A) Subcellular localization of Rrp36p. The RRP36::3HA strain transformed with a plasmid expressing GFP-Nop1p was grown exponentially, and cell samples were treated for fluorescence microscopy. The two rightmost columns show merged images. (B) Sedimentation profile of Rrp36p-3HA on a sucrose gradient. A total extract prepared from RRP36::3HA cells growing exponentially was sedimented through a sucrose gradient, and 18 fractions were collected. The corresponding A₂₅₄ profile is displayed with the characteristic annotated peaks. One-half of each fraction was precipitated by TCA, and Rrp36p-3HA was detected in these samples by Western blotting using anti-HA antibodies. RNAs contained in the other half of each fraction were purified, and specific molecules were detected by Northern blotting using the indicated probes (see Fig. 3C and Table S1 in the supplemental material for details).