Homo sapiens C/D box snoRNA U103. This snoRNA was first cloned from a rat cDNA library, and its human orthologue identified by database search (Vitali et al., 2003). Two perfect copies, as well as the C/D box snoRNA HBII-251, reside in the same host gene (PUM1). U103 is predicted to guide the 2'O-ribose methylation of G601 of 18S rRNA (same target as HBII-251) . Note that the published sequence of U103 differs from the genomic sequence by 2 nts near its 3' end.