PCNA and hepatocellular carcinoma: However, after transfecting the NEDD8 plasmid into NEDD8-/- HCC cell lines, compared to the control group, the shNUB1 group showed increased PCNA NEDDylation, decreased PCNA K48-linked polyubiquitination, and increased PCNA expression, whereas the Flag-NUB1 group showed the opposite results (Fig. 6F and Supplementary Fig. 4F).