GUIDING RIBOSE METHYLATION OF RIBOSOMAL-RNA

Eukaryotic rRNAs contain a complex set of ribose-methylated nucleotide s. Why are these nucleotides modified and how are they selected? A lar ge family of small nucleolar RNAs (snoRNAs) with long complementaritie s to sites of rRNA methylation has been recently found to guide such m odifications, opening up a direct approach to the study of their elusi ve function. Ribose methylation can also be targeted to non-rRNA seque nces by tailored snoRNA guides, possibly providing a highly selective tool for altering gene expression at the post-transcriptional level.