The clathrin-binding domain of CALM and the OM-LZ domain of AF10 are sufficient to induce acute myeloid leukemia in mice

The t(10;11)(p13-14;q14-21) translocation, giving rise to the CALM–AF10 fusion gene, is a recurrent chromosomal rearrangement observed in patients with poor prognosis acute myeloid leukemia (AML). Although splicing of the CALM–AF10 fusion transcripts has been described in AML patients, the contribution of different CALM and AF10 domains to in vivo leukemogenesis remains to be defined. We therefore performed detailed structure-function studies of the CALM–AF10 fusion protein. We demonstrate that fusion of the C-terminal 248 amino acids of CALM, which include the clathrin-binding domain, to the octapeptide motif–leucine-zipper (OM-LZ) domain of AF10 generated a fusion protein (termed CALM–AF10 minimal fusion (MF)), with strikingly enhanced transformation capabilities in colony assays, providing an efficient system for the expeditious assessment of CALM–AF10-mediated transformation. Leukemias induced by the CALM–AF10 (MF) mutant recapitulated multiple aspects of full-length CALM–AF10-induced leukemia, including aberrant Hoxa cluster upregulation, a characteristic molecular lesion of CALM–AF10 leukemias. In summary, this study indicates that collaboration of the clathrin-binding and the OM-LZ domains of CALM–AF10 is sufficient to induce AML. These findings further suggest that future approaches to antagonize CALM–AF10-induced transformation should incorporate strategies, which aim at blocking these key domains.