SF3B1 is an essential component in U2 snRNP and crucial for RNA splicing. (A) SF3B1 lies within the U2 snRNP and interacts with the 5′ and 3′ adjacent sites of the BPS, a critical splice site motif. PY tract, polypyrimidine tract. (B) A schematic of the stepwise process of pre-mRNA splicing.