Background: CSTF50 is one of three subunits that comprise the cleavage stimulation factor (CSTF) complex. CSTF is part of the polyadenylation machinery that adds adenylate residues to the 3’-ends of eukaryotic pre-mRNAs. In the CSTF complex, CSTF50 interacts with CSTF77 (CSTF3), and CSTF64 (CSTF2).