(2)The procedures of polyA formation (1CPSF recognizes AAUAAA and binds to it (2)Cf cleavages at the specific point of 11 30 nt downstream aauaaa (3)poly(A) polymerase未端腺苷转移酶 adds a to form poly(a) (4)poly(A)is combined with PBP◼ (1) CPSF recognizes AAUAAA and binds to it; ◼ (2) Cf cleavages at the specific point of 11 －30 nt downstream AAUAAA; ◼ (3) poly(A) polymerase [末端腺苷转移酶] adds A to form poly(A); ◼ (4) poly(A) is combined with PBP. (2) The procedures of PolyA formation