PRPF8 is the only U5 snRNP protein where recurrent somatic mutations have been linked to cancer, joining the ranks of spliceosome factors such as U2AF1 and SF3B1 as frequently mutated in certain types of human cancers, in particular leukemias (Grosso et al., 2008; Yoshida and Ogawa, 2014; Visconte et al., 2019). The gene discussed is SF3B1; the disease is leukemia.