FIG. 4.

In the absence of Nog1, pre-rRNAs accumulate in the nucleolus. (A) Intranuclear distribution of the preribosomal particles in Nog1- or Nog2-depleted cells was determined by FISH with a probe specific for the ITS2 sequence. DNA was stained with the DAPI (4′,6′-diamidino-2-phenylindole) fluorescent dye. Arrowheads, position of the nucleoplasm. (B) ITS2 containing pre-RNAs were detected by electron microscopy in situ hybridization in cells depleted of Nog1 or Nog2 by growth on glucose for 14 h, and the labeling densities of the nucleolus and the nucleoplasm were determined. One-to-one comparisons with the wild-type (WT) strain showed significant differences (∗∗, P < 0.01; ∗∗∗, P < 0.001). The nucleoplasmic labeling in Nog2-depleted cells is also significantly higher (P < 0.001) than that in cells lacking Nog1.