Human Nop5/Nop58 is a component common to the box C/D small nucleolar ribonucleoproteins

We have identified an apparent human homolog of the yeast Nop5/Nop58 protei n. hNop5/Nop58 codes for a protein of predicted molecular weight 59.6 kDa a nd is 46.8% identical to Saccharomyces cerevisiae Nop5/Nop58. Immunofluores cent staining with antibodies against hNop5/Nop58 indicate that it is local ized primarily to the nucleolus, and coimmunoprecipitation from nuclear ext racts demonstrates that hNop5/Nop58 interacts with the box C/D family of sn oRNAs. Thus, hNop5/Nop58 is a common component of the box C/D snoRNPs, and joins fibrillarin as the second such component identified and characterized in metazoans.