Homo sapiens C/D box snoRNA U102. This snoRNA was identified by Vitali et al. (2003) in the systematic search for C/D box hallmarks in the introns of ribosomal protein genes. U102 gene resides in intron 3 of the ribosomal protein L21 gene, whereas intron 5 of the same gene hosts the H/ACA box snoRNA ACA27. U102 is predicted to guide the 2'O-ribose methylation of G4020 of 28S rRNA.