This family is the dimerisation domain, at the N-terminal, of a family of cleavage stimulation factor subunit 1 proteins from eukaryotes. This domain allows for homodimerisation such that the functional state of CSTF1 is a heterohexamer. The cleavage stimulation factor (CstF) complex is composed of three subunits and is essential for pre-mRNA 3'-end processing. CstF recognises U and G/U-rich cis-acting RNA sequence elements and helps to stabilise the cleavage and polyadenylation specificity factor (CPSF) at the polyadenylation site as required for productive RNA cleavage [1].

1: Hexameric architecture of CstF supported by CstF-50 homodimerization domain structure. Moreno-Morcillo M, Minvielle-Sebastia L, Mackereth C, Fribourg S; RNA. 2011;17:412-418. PMID:21233223