ZUP1 and cancer: While DUBs have been implicated inthe regulation of many biological processes and are involved in pathogenicpathways,4,5 their function and natural substrates arelargely underexplored.8 Among seven knownand putative DUB families encoded by the human genome, the ubiquitin-specificproteases (USPs) comprise the largest subfamily (50+ proteins) witha conserved protease domain possessing a catalytic cysteine.9−11 Recently, USPs have emerged as novel targets for cancer treatmentdue to their over-expression and activation in various malignant tumors.12