Mutation of the spliceosome components SF3B1 and U2AF1 are recurrent driver events in many cancer types including chronic lymphoblastic leukemia, myelodysplastic syndrome, uveal melanoma and breast cancer (Ellis et al., 2012; Harbour et al., 2013; Imielinski et al., 2012; Papaemmanuil et al., 2011; Wang et al., 2011; Yoshida et al., 2011). Here, U2AF1 is linked to breast carcinoma.