Fig. 2. U3 and the snR10 (Box C/D and Box H/ACA snoRNAs, respectively) are readily detected in the yeast nucleolus by fluorescence in situ hybridization (FISH). (A) U3 and snR10 localize to crescent-shaped nucleoli of S. cerevisiae as revealed by hybridization with Cy3-labeled, antisense probes against U3 or snR11 (RNA panel). The merged image shows that the snoRNA signals (detected by FISH) are directly adjacent to the nucleoplasmic DNA detected by DAPI staining of the same cells. (B) Colocalization of snoRNAs with the nucleolar marker protein, Nop1 (fibrillarin). A combination of FISH (to detect U3 snoRNA) and immunofluorescence (to detect Nop1 protein) was performed. The merge image indicates an overlay of U3 snoRNA and Nop1 protein. DIC, differential interference contrast. Arrowheads point to a nucleolus.