One of the multiple factors required for polyadenylation and 3'-end cleavage of mammalian pre-mRNAs (PubMed:10669729). May be responsible for the interaction of CSTF with other factors to form a stable complex on the pre-mRNA (PubMed:10669729). Homodimer (PubMed:10669729). The CSTF complex is composed of CSTF1 (50 kDa subunit), CSTF2 (64 kDa subunit) and CSTF3 (77 kDa subunit) (PubMed:10669729). Interacts (via repeats WD) directly with CSTF3 (PubMed:10669729). Interacts (via repeat WD6) with BARD1 (PubMed:10477523). Interacts with ERCC6 (PubMed:26030138). N-terminus mediates homodimerization. The N-terminus is blocked.