CPSF3 and hepatocellular carcinoma: The extensive rearrangements of mCF/HCC and CPSF73 for catalyzing the processing are demonstrated by a recent cryo-EM study of histone recombinant machinery (Figure 5A–C), which is the only structure so far that shows the endonuclease CPSF73 in an open, active state, in which CPSF73 captures the pre-mRNA in its active site, ready to be cleaved (Figure 5D) [30].