SF3B1 and cancer: For example, cancer-associated mutations in the HEAT domains of SF3B1 [1] were proposed to lead to changes in the positioning of other RNA-binding proteins, including the 65 kilodalton (kD) subunit of the U2 small nuclear ribonucleoprotein auxiliary factor (U2AF65), ultimately altering interactions with pre-mRNAs [5] and the selection of lariat branch points and 3′ss [6,7,8].