Fig. 2

a Superposition of NPM1 genomic structure and protein features. NPM1.1 and NPM1.3 are two splices variants resulting from the use of alternative codons. The two isoforms have different expression levels and localization. Ac Acidic domain, NES nuclear export signal, MB putative metal binding domain, NLS nucleus localization signal, NoLS Nucleolar localization signal. b Schematic structure of NPM proteins from human (not to scale). All proteins share a core, hydrophobic domain (blue) responsible for oligomerization and chaperone activity, followed by an acidic domain required for ribonuclease activity. A basic domain implicated in nucleic acid binding is common to NPM1 and NPM2, but absent in NPM3. Finally, only NPM1 exhibits a C-terminal aromatic stretch require for its nucleolar localization. In addition, NPM members harbor nuclear-localization signals (NLS), nucleolar-localization signal (NoLS), nuclear export signal (NES) and acidic clusters (a). c Simplified representation of the phylogenetic relationship within the NPM family. Inferred from [4]. The dendrogram reveals a clustering of sequences by type, rather than by species, and identifies NPM2 and NPM3 as polyphyletic groups