Involved in the early to middle stages of 60S ribosomal subunit biogenesis. Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles. Required for the biogenesis of box C/D snoRNAs such U3, U8 and U14 snoRNAs. Part of a large pre-ribosomal ribonucleoprotein (RNP) complex, that consists of at least 62 ribosomal proteins, 45 nonribosomal proteins and both pre-rRNA and mature rRNA species. Within this complex directly interacts with TCOF1 in an RNA-independent manner. Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles; the core proteins SNU13, NOP56, NOP58 and FBL assemble stepwise onto the snoRNA. Interacts NOP1 and NOP58. Interacts with NUFIP1, RUVBL1 and RUVBL2; RUVBL1:RUVBL2 seem to bridge the association of NOP56 with NUFIP1. The disease is caused by variants affecting the gene represented in this entry. Caused by large hexanucleotide CGCCTG repeat expansions within intron 1. These expansions induce RNA foci and sequester the RNA-binding protein SRSF2. In addition, the transcription of MIR1292, a microRNA gene located just 19 bp 3' of the GGCCTG repeat, is significantly decreased. Belongs to the NOP5/NOP56 family. Extended N-terminus.