Nucleophosmin is involved in diverse cellular processes such as ribosome biogenesis, centrosome duplication, protein chaperoning, histone assembly, cell proliferation, and regulation of tumor suppressors TP53/p53 and ARF. Nucleophosmin binds ribosomes presumably to drive ribosome nuclear export. Nucleophosmin associates with nucleolar ribonucleoprotein structures and binds single-stranded nucleic acids. Nucleophosmin acts as a chaperonin for the core histones H3, H2B and H4. A chromosomal aberration in nucleophosmin is found in a form of non-Hodgkin lymphoma.