One of the multiple factors required for polyadenylation and 3'-end cleavage of mammalian pre-mRNAs. This subunit is directly involved in the binding to pre-mRNAs (By similarity). The CSTF complex is composed of CSTF1 (50 kDa subunit), CSTF2 (64 kDa subunit) and CSTF3 (77 kDa subunit). CSTF2 directly interacts with CSTF3, SYMPK and RPO2TC1. Interacts with HSF1 in heat-stressed cells (By similarity). Interacts with CPSF2, CPSF3 and FIP1L1. Interacts with DDX1 (By similarity). Localized with DDX1 in cleavage bodies.