Late-acting factor in the nuclear maturation of 60S ribosomal subunits, which is required for normal acquisition of export competence. Required for the export of the large subunit. Acts to stimulate the RNase activity of the exosome complex, and may recruit the exosome to 7S pre-rRNA for processing. Associates with numerous RNAs including the 27S and 7S pre-rRNAs and the box H/ACA snoRNA snR37. Also interacts (via N-terminal region) with the mature 25S rRNA and the mature 5.8S rRNA. Interacts with CBF5, FPR3, FPR4, NOP2, PIH1, RRN3, RRP6 and PAP2. Interacts with pre-60S ribosomal particles. Does not shuttle from the nucleus to the cytoplasm (PubMed:16043506). Inhibition of cell growth. Defects in processing of the rRNA components of the 60S ribosomal subunit and accumulation of the corresponding polyadenylated pre-rRNAs. Some delay in the maturation of the 35S primary transcript and 32S pre-rRNA. Delay in 20S pre-rRNA formation and a severe delay in mature 25S and 5.8S rRNA formation, with accumulation of the 35S, 32S, 27S, 26S and 7S pre-rRNAs and a 5' extended form of the 25S rRNA. Complete loss of synthesis of the mature 25S rRNA. Appearance at a low level of aberrant 23S species. Shorter 18S and 5.8S rRNA at the 5' end. Imbalance in the 40S:60S ratio and defects in progression beyond the 27S stage of 25S rRNA maturation during 60S biogenesis. Decreased ribosomes and polysomes and presence of halfmers. Present with 1600 molecules/cell in log phase SD medium. Belongs to the NOP53 family.