Studies of SF3B1 in AS have focused on disease-causing mutant forms in CLL and MDS, providing gain-of-function evidences of mutant isoforms in alternative usage of BPS and cryptic 3′SS or loss-of-function evidences such as reduced interaction with SUGP1 [21,29,30,31]. Here, SUGP1 is linked to B-cell chronic lymphocytic leukemia.