Component of the cleavage and polyadenylation specificity factor (CPSF) complex that play 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. CPSF4 binds RNA polymers with a preference for poly(U). Component of the cleavage and polyadenylation specificity factor (CPSF) complex, composed of CPSF1, CPSF2, CPSF3, CPSF4 and FIP1L1. Interacts with FIP1L1. (Microbial infection) Interacts with influenza A virus NS1 blocks processing of pre-mRNAs, thereby preventing nuclear export of host cell mRNAs. May be due to a competing acceptor splice site. Belongs to the CPSF4/YTH1 family.