XB-IMG-119021
Xenbase Image ID: 119021
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Figure 9. Localization of U4 snRNA to nucleoli and Cajal bodies after cytoplasmic and nuclear injections. Fluorescein-labeled synthetic transcripts of wild-type U4 snRNA (WT U4), a U4 mutant unable to base pair with U6 snRNA (Δ1–18/56–63), the NoLE mutant of U4 (ΔNHPX/15.5 kD), or wild-type U3 snoRNA (WT U3) were injected into Xenopus oocytes. Either 5 h after cytoplasmic injection or 1.5 h after nuclear injection, nuclear spreads were prepared and analyzed by phase contrast (PC) or fluorescence microscopy (FL, green). Nucleoli can be distinguished from other nonchromosomal nuclear bodies because they contain rDNA visualized by staining (DAPI, blue). Cajal bodies are indicated by arrows; they do not contain rDNA (DAPI negative) and often are associated with B-snurposomes (Gall et al., 1999 and references therein). After cytoplasmic injection, both wild-type U4 as well as mutant Δ1–18/56–63 localize weakly to nucleoli (compare DAPI with FL) and exhibit a much stronger preference to localize to Cajal bodies (arrows). The same observations were made for U5 snRNA (Lange, 2003). In contrast, U4 NoLE mutant ΔNHPX/15.5 kD does not reveal any signals in either nuclear compartment. U3 snoRNA after cytoplasmic injection strongly stained nucleoli but not Cajal bodies, unlike the pattern for U4 or U5. After nuclear injection, as shown before (Fig. 3), wild-type U4 and mutant Δ1–18/56–63 preferentially localized to nucleoli which are stained strongly (compare DAPI with FL); Cajal bodies are stained weakly and indicated by arrows (no DAPI signal). U3 snoRNA, similar to U4 snRNA after injection into Xenopus oocyte nuclei, can weakly stain Cajal bodies but strongly localizes to nucleoli (Lange and Gerbi, 2000). A synthetic negative control RNA after nuclear or cytoplasmic injection did not stain either nucleoli or Cajal bodies (Lange and Gerbi, 2000; Lange, 2003). Bar, 10 μm. Image published in: Gerbi SA et al. (2003) Copyright © 2003, The Rockefeller University Press. Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View |