title: A CALM-derived nuclear export signal is essential for CALM-AF10-mediated leukemogenesis.
abstract: The t(10;11) chromosomal translocation gives rise to the CALM-AF10 fusion gene and is found in patients with aggressive and difficult-to-treat hematopoietic malignancies. CALM-AF10-driven leukemias are characterized by HOXA gene up-regulation and a global reduction in H3K79 methylation. DOT1L, the H3K79 methyltransferase, interacts with the octapeptide/leucine zipper domain of AF10, and this region has been shown to be necessary and sufficient for CALM-AF10-mediated transformation. However, the precise role of CALM in leukemogenesis remains unclear. Here, we show that CALM contains a nuclear export signal (NES) that mediates cytoplasmic localization of CALM-AF10 and is necessary for CALM-AF10-dependent transformation. Fusions of the CALM NES (NES(CALM)-AF10) or NES motifs from heterologous proteins (ABL1, Rev, PKIA, APC) in-frame with AF10 are sufficient to immortalize murine hematopoietic progenitors in vitro. The CALM NES is essential for CALM-AF10-dependent Hoxa gene up-regulation and aberrant H3K79 methylation, possibly by mislocalization of DOT1L. Finally, we observed that CALM-AF10 leukemia cells are selectively sensitive to inhibition of nuclear export by Leptomycin B. These findings uncover a novel mechanism of leukemogenesis mediated by the nuclear export pathway and support further investigation of the utility of nuclear export inhibitors as therapeutic agents for patients with CALM-AF10 leukemias.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27710, USA.
authors.forename: Amanda E
authors.initials: AE
authors.lastname: Conway
authors.forename: Paula B
authors.initials: PB
authors.lastname: Scotland
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Lavau
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Wechsler
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D016026:Bone Marrow Transplantation; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D002478:Cells, Cultured; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D007942:Leukemia, Experimental / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D034041:Monomeric Clathrin Assembly Proteins / Q000502:physiology*; D049790:Nuclear Export Signals / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D015996:Survival Rate
chemical_list: C114359:AF10-CALM fusion protein, human; D000903:Antibiotics, Antineoplastic; D005231:Fatty Acids, Unsaturated; D018398:Homeodomain Proteins; D034041:Monomeric Clathrin Assembly Proteins; D049790:Nuclear Export Signals; D015514:Oncogene Proteins, Fusion; C573094:PICALM protein, mouse; C088144:HoxA protein; C038753:leptomycin B