Nucleophosmin, a multifunctional nucleolar organizer with a role in DNA repair

Nucleophosmin (NPM1) is a mostly nucleolar protein with crucial functions in cell growth and homeostasis, including regulation of ribosome biogenesis and stress response. Such multiple activities rely on its ability to interact with nucleic acids and with hundreds of proteins, as well as on a dynamic subcellular distribution. NPM1 is thus regulated by a complex interplay between localization and interactions, further modulated by posttranslational modifications. NPM1 is a homopentamer, with globular domains connected by long, intrinsically disordered linkers. This configuration allows NPM1 to engage in liquid-liquid phase separation phenomena, which could underlie a key role in nucleolar organization. Here, we will discuss NPM1 conformational and functional versatility, emphasizing its emerging, and still largely unexplored, role in DNA damage repair. Since NPM1 is altered in a subtype of acute myeloid leukaemia (AML), we will also present ongoing research on the molecular mechanisms underlying its pathogenic role and potential NPM1-targeting therapeutic strategies.