CPSF plays a key role in pre-mRNA 3'-end formation, recognizing the AAUAAA signal sequence and interacting with poly(A)polymerase and other factors to bring about cleavage and poly(A) addition. This subunit is involved in the RNA recognition step of the polyadenylation reaction. Component of the CPSF complex, at least composed of CPSF160, CPSF100, CPSF73-I, CPSF73-II, CPSF30, FY and FIPS5. Forms a complex with cleavage and polyadenylation specificity factor (CPSF) subunits FY, CPSF30, CPSF73-I, CPSF 73-II and CPSF100. Belongs to the CPSF1 family.