Required for the biogenesis of box C/D snoRNAs such as U3, U8 and U14 snoRNAs (PubMed:15574333, PubMed:17636026, PubMed:19620283, PubMed:34516797). Part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. During the assembly of the SSU processome in the nucleolus, many ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA and work in concert to generate RNA folding, modifications, rearrangements and cleavage as well as targeted degradation of pre-ribosomal RNA by the RNA exosome (PubMed:34516797). Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) complexes that function in methylation of multiple sites on ribosomal RNAs (rRNAs) and messenger RNAs (mRNAs) (PubMed:39570315). {ECO:0000269|PubMed:15574333, ECO:0000269|PubMed:17636026, ECO:0000269|PubMed:19620283, ECO:0000269|PubMed:34516797, ECO:0000269|PubMed:39570315}. This is the function of ENSG00000055044 (NOP58, NOP58 ribonucleoprotein).