USP5 and cancer: The deletion of Usp5 (also called isopeptidase T, IsoT), a yeast Ubp14 ortholog in human, also results in the accumulation of polyUb chains (20, 21) and has been implicated in several diseases, especially cancer, by stabilizing different target proteins, such as c-Maf protein, FoxM1, and p53 protein (21, 22).