BAP1 and acute myeloid leukemia: Thus, ASXL1 truncation mutations confer gain-of-function in the pathogenesis of myeloid malignancies by increasing BAP1 DUB activity, and reducing BAP1 activity ameliorates the abnormal hematopoietic phenotypes due to mutated Asxl1. Because most ASXL2 mutations are out-of-frame frameshift mutations in exons 11 and 12, at least in AML with t(18;21) [12], the BAP1 binding region in ASXL2 is also unaffected, although it remains to be determined whether truncated ASXL2-BAP1 complexes exhibit enhanced DUB activity.