FIG. 6.

Summary of box C/D snoRNP assembly. The box C/D snoRNA, bound to an rRNA target sequence (methylation site is indicated by a circle), is shown here schematically with the conserved nucleotides of the box C/D motif represented as in Fig. 1A. The specific sequence requirements for the hierarchical assembly of the box C/D snoRNP are indicated. The 15.5K protein, the primary snoRNA binding protein, binds to the internal loop, while the remaining box C/D snoRNP proteins bind the 15.5K-snoRNA complex, specifically recognizing the conserved sequence of stem II. Fibrillarin (fibr.) and NOP56 and NOP58, TIP48, and TIP49 are grouped to indicate the connected nature of their association with the snoRNP.