SF3B1, a key U2 spliceosome component, regulates the early splicing stages by recognizing the branch point intronic sequence, which is affected by hotspot mutations common in patients with chronic lymphocytic leukemia (CLL) and myelodysplastic syndromes (MDSs) and has been associated with aberrant splicing in hematological malignancies (3–7). The gene discussed is SF3B1; the disease is B-cell chronic lymphocytic leukemia.