Schematic of MLL-GPHN and its mutants used in this study. The chimeric gene in leukemia is MLL-GPHN full. MT indicates DNA methyltransferase homology domain; SET, SET domain; MoaB, MogA, and MoeA, regions in GPHN with sequence similarities to the respective Escherichia coli proteins involved in molybdenum cofactor biosynthesis. Arrows indicate the fusion site. Numbers refer to amino acid positions in wild-type MLL or GPHN. The black bar indicates the tubulin-binding site of GPHN.