Required for endonucleolytic cleavage during polyadenylation-dependent pre-mRNA 3'-end formation (By similarity). Functions in gametophyte, embryo and postembryotic development (PubMed:18971429). Interacts with PCFS4 and SYM5. Forms a complex with cleavage and polyadenylation specificity factor (CPSF) subunits CPSF30, CPSF100, PCFS1, PCFS4, PCFS5, CPSF160 and FY. Belongs to the Clp1 family. Clp1 subfamily.