RIBC2 and acute myeloid leukemia: Furthermore, an ‘oncogenic’ R107L TRIB1 mutation in the pseudokinase domain has been identified in a Down syndrome-related AML [7]; this Arg residue is broadly conserved across the TRIB pseudokinases (Figure 3A, asterisk), but is a Leu residue in the canonical kinase PKA, where it packs up against hydrophobic residues in the C-terminal tail [39].