RNA-binding protein required for the maturation of box H/ACA snoRNPs complex and ribosome biogenesis. During assembly of the H/ACA snoRNPs complex, it associates with the complex and disappears during maturation of the complex and is replaced by GAR1 to yield mature H/ACA snoRNPs complex. Acts as a competitive binder for CBF5 probably required to prevent non-cognate RNAs from being loaded during transport of the particle by inducing a non-productive conformation of CBF5 (By similarity). During assembly of the complex, component of the small nucleolar ribonucleoprotein particles containing H/ACA-type snoRNAs (H/ACA snoRNPs) which contains CBF5, NAF1, NHP2 and NOP10 proteins (By similarity). Interacts with SHQ1. Interacts directly with CBF5. Interacts with hyperphosphorylated C-terminal domain (CTD) of RNA polymerase II large subunit (RPB1) (By similarity). Mostly present in the nucleoplasm. Absent from the nucleolus (By similarity). The central region (136-221) reveals a striking structural homology with the core domain of GAR1. Belongs to the NAF1 family.