Component of the cleavage and polyadenylation specificity factor (CPSF) complex that 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 (By similarity). Component of the cleavage and polyadenylation specificity factor (CPSF) complex, composed of at least Clp, Cpsf73, Cpsf100 and Cpsf160. Belongs to the CPSF1 family.