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. Has endonuclease activity. Binds RNA polymers with a preference for G- and/or C-rich clusters. Binds single-stranded DNA non-specifically. Component of the cleavage and polyadenylation specificity factor (CPSF) complex, composed of at least Clp, Cpsf73, Cpsf100 and Cpsf160. During oogenesis, expression is detected in the germarium, in nurse cells, in the oocyte, and in the somatically derived follicular epithelial cells (at protein level). At oogenesis stage 12, nurse cells degenerate and their content is transferred into the oocyte. In larvae, expressed in all organs and disks (at protein level). In the larval salivary gland, expression is initially confined to cells at the anterior end but later expands throughout the entire gland (at protein level). Expressed both maternally and zygotically. During embryogenesis expressed only at transcript level. Expressed in larvae (at protein level), pupae and adults. Initial embryonic expression is maternally derived, then gradually decreases until third-instar larvae when there is a burst of zygotic expression. Most of the female expression is ovarian (at protein level). The N-terminal region containing the five C3H1-type zinc fingers is essential for endonuclease activity. The C-terminal region containing the two CCHC-type zinc fingers confers a binding preference for RNAs that contain G- and/or C-rich clusters. Extended N-terminus.