PIH1D1 is a phylogenetically conserved protein essential for efficient processing of pre-rRNA through its association with a class of small nucleolar RNAs (snoRNAs) during ribosomal biogenesis. SnoRNAs are associated in ribonucleoprotein particles localized to the nucleolus. Nop17 is a 290 amnio acid unstable protein that is stabilized through an interaction with HSP 90?/∫. Nop17 interacts with a core box C/D snoRNP protein Nop58, indicating a function of Nop17 in mediating the nucleolar retention or proper assembly of the box C/D snoRNP. A mutation in NOP17 gene may lead to a temperature-sensitive phenotype along with delocalization of key Nop proteins that are essential for snoRNP assembly.