Required for 60S ribosomal subunit biogenesis (By similarity). Core component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles. Required for the biogenesis of box C/D snoRNAs such as U3, U8 and U14 snoRNAs (By similarity). 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 with NOLC1/Nopp140. Interacts with NUFIP1, RUVBL1 AND RUVBL2; RUVBL1:RUVBL2 seem to bridge the association of NOP58 with NUFIP1. Interacts with PIH1D1 (By similarity). Sumoylation is essential for high-affinity binding to snoRNAs. Belongs to the NOP5/NOP56 family.