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 (PubMed:10864044). Interacts with NOLC1/Nopp140. Interacts with NOPCHAP1, NUFIP1, RUVBL1 and RUVBL2; NOPCHAP1 bridges the association of NOP58 with RUVBL1:RUVBL2 and NUFIP1. Interacts with PIH1D1. Sumoylation is essential for high-affinity binding to snoRNAs. Belongs to the NOP5/NOP56 family.