In the SF3B1-mutated (SF3B1m) cancer patient samples including chronic lymphocytic leukemia, breast cancer, and melanoma, the mutations are between Y623 and G742 (Darman et al., 2015), within the HEAT domain, which is required for interaction with the ATPase Prp5 and branch site selection (Tang et al., 2016). The gene discussed is SF3B1; the disease is B-cell chronic lymphocytic leukemia.