Co-IP and western blot assays showed that compared with the control group, NUB1 knockdown promoted PCNA NEDDylation and inhibited PCNA K48-linked polyubiquitination, thereby upregulating the protein levels of PCNA in HCC cells, whereas NUB1 overexpression inhibited PCNA NEDDylation and increased PCNA K48-linked polyubiquitination, thereby decreasing PCNA protein levels in HCC cells (Fig. 6B and Supplementary Fig. 4B). Here, PCNA is linked to hepatocellular carcinoma.