Nucleophosmin (NPM; also known as B23, numatrin or NO38) is a highly conserved phosphoprotein that belongs to nucleoplasmin/nucleophosmin family of nuclear chaperones. It binds ribosome to drive ribosome nuclear export and has been associated with nucleolar ribonucleoprotein structures. The NPM gene is also known for its fusion with the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase. The NPM portion contributes to transformation by providing a dimerization domain, which results in activation of the fused kinase.
