Anti-nucleophosmin 1 antibodies are used in the immunodetection of the protein encoded by the NPM1 gene. In humans, the canonical protein has a reported length of 294 amino acid residues and a mass of 32.6 kDa. Its subcellular localization is in the nucleus and cytoplasm. Alternative splicing is reported to yield 3 different isoforms for this protein. A member of the Nucleoplasmin protein family, it is known to be involved in diverse cellular processes such as ribosome biogenesis, centrosome duplication, protein chaperoning, histone assembly, cell proliferation, and regulation of tumor suppressors p53/TP53 and ARF. Post-translational modifications have been described, including ubiquitination, sumoylation, acetylation and phosphorylation. Other names for this target antigen include NPM, nucleophosmin, nucleolar protein NO38, nucleophosmin (nucleolar phosphoprotein B23, numatrin), nucleophosmin/nucleoplasmin family, member 1, and B23.