SF3B1 and B-cell chronic lymphocytic leukemia: Recently, RNA-sequencing (RNA-Seq) analysis of CLL, breast cancer and UM showed that a global splicing defect in SF3B1-mutated tumours consists in usage of cryptic 3′ss (hereafter called AG′) located 10 to 30 bases upstream of normal 3′ss, yet the underlying mechanism has remained poorly understood.