RNA-binding component of the cleavage and polyadenylation factor (CPF) complex, which plays a key role in polyadenylation-dependent pre-mRNA 3'-end formation and cooperates with cleavage factors including the CFIA complex and NAB4/CFIB. Negative regulator of poly(A) synthesis. Component of the APT complex, which may be involved in polyadenylation-independent transcript 3'-end formation. REF2 is required for 3'-end formation of snoRNAs