In the analogous mammalian cleavage factor (mCF) and in the histone cleavage complex (HCC), the CPSF73/100 dimer interacts directly with the HEAT repeat protein Symplekin, forming a catalytic core shared between the two machineries (Kolev and Steitz, 2005; Michalski and Steiniger, 2015; Sullivan et al., 2009). This evidence concerns the gene CPSF3 and hepatocellular carcinoma.