Prevalent U2AF1 somatic mutations, including U2AF1S34F, occur in hematopoietic malignancies including myelodysplastic syndrome (MDS), AML, and chronic myelomonocytic leukemia (CMML), as well as in some solid tumors such as lung adenocarcinoma115–117. Here, U2AF1 is linked to chronic myelomonocytic leukemia.