Cellular component

A ribonucleoprotein complex that contains an RNA molecule of the snoRNA family and associated proteins. Many are involved in a step of processing of rRNA molecules: cleavage, 2'-O-methylation, or pseudouridylation, but other RNA types can be targets as well. The majority fall into one of two classes, box C/D type or box H/ACA type, which are conserved across eukaryotes and archaea. Other members include the telomerase RNA and the ribonuclease MRP RNA.

Note that 'nucleolar' in the name acronym 'snoRNA' is part of the RNA family designation 'small nucleolar', and does not reflect the location of the complex. Both box C/D type and box H/ACA RNAs are found in Archaea (where they are referred to as sRNAs) as well as in Eukaryota. In eukaryotes, box H/ACA RNAs are found in both nucleolar-localized snoRNP complexes and in Cajal body-localized scaRNP complexes.