Client-loading PAQosome/R2TP complex cofactor that selects NOP58 to promote box C/D small nucleolar ribonucleoprotein (snoRNP) assembly. Acts as a bridge between NOP58 and the R2TP complex via RUVBL1:RUVBL2. Interacts with NOP58, RUVBL1 and RUVBL2; the interactions are direct and NOPCHAP1 bridges the association of NOP58 with RUVBL1:RUVBL2 even in absence of snoRNAs. The interactions with RUVBL1 and RUVBL2 are disrupted upon ATP binding.