It was shown that the C-terminal domain of the AML-linked NPM1 mutant A form, which lacks both Trp288 and Trp290, is unfolded and unable to bind rDNA G-quadruplexes, while the reinsertion of the two tryptophan residues was sufficient to restore the correct folding, G-quadruplex binding and nucleolar localization [40, 116]. Here, NPM1 is linked to acute myeloid leukemia.