[Mammalian 87 small nucleolar RNA and its host gene]

The vast majority of C/D box small nucleolar RNAs (snoRNAs) direct site-specific methylation of ribose in rRNA. New mammalian snoRNA U87 belongs to the C/D family and is involved in ribose methylation of guanylic acid residue (position 3468) in 28S rRNA. A host gene harboring the U87 snoRNA gene in its intron was described for rodents and humans. In humans it has three neighbouring transcription start sites whereas in rat there are many scattered start sites. The transcript of this gene possesses some characteristic features of an mRNA (splicing, polyadenylation and cytoplasmic localization) but lacks long open reading frames and the degree of its conservation is much less than that of other host gene mRNAs. Such low conservation is discussed in the context of functional significance of exonic sequences of the gene.